dolichols and dolichol-monophosphate

The addition of oligosaccharide to asparagine residues of soluble and membrane-associated proteins in eukaryotic cells involves a polyisoprenoid lipid carrier, dolichol. In Chinese hamster ovary cells, the major isomer of this polyisoprenol has 19 isoprenyl units, the terminal one being saturated. Our laboratory has developed a procedure to analyze the levels and nature of the cell's dolichyl derivatives. Chinese hamster ovary cells contain predominately activated, anionic dolichol derivatives, such as oligosaccharyl pyrophosphoryldolichol, monoglycosylated phosphoryldolichols, and dolichyl phosphate. Our studies show that in growing cells there is continual synthesis of total dolichol. Also, preliminary data suggest there is no catabolism or secretion of this lipid. The level of dolichyl phosphate did not change significantly under a variety of conditions where the levels of enzyme activities utilizing dolichyl phosphate did change. These results suggested that these enzymes had access to the same pool of dolichyl phosphate and had similar Km values for this lipid.

Topics: Amino Acid Sequence; Animals; Asparagine; CHO Cells; Consensus Sequence; Cricetinae; Cricetulus; Dolichol Phosphates; Dolichols; Glycosylation; Molecular Sequence Data; Phosphorylation; Protein Processing, Post-Translational; Tunicamycin

This review deals with the structure and addition of the different types of oligosaccharides to asparagine residues in proteins. This process occurs in several steps, first an oligosaccharide which contains N-acetylglucosamine mannose and glucose is built up joined to dolichyl diphosphate. The oligosaccharide is then transferred to a polypeptide chain, loses its glucose, and is modified by removal of some monosaccharides and addition of others giving rise to a variety of saccharides.

Topics: Acetylglucosamine; Acetylglucosaminidase; Animals; Asparagine; Cells, Cultured; Dolichol Phosphates; Dolichols; Fungi; Glucose; Glycoproteins; Humans; Insecta; Mannose; Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; Models, Biological; Oligosaccharides; Peptides; Plants; Polyisoprenyl Phosphates; Viruses

Oligosaccharyl phosphates (OSPs) are hydrolyzed from oligosaccharide-diphosphodolichol (DLO) during protein N-glycosylation by an uncharacterized process. An OSP-generating activity has been reported in vitro, and here we asked if its biochemical characteristics are compatible with a role in endoplasmic reticulum (ER)-situated DLO regulation. We demonstrate a Co(2+)-dependent DLO diphosphatase (DLODP) activity that splits DLO into dolichyl phosphate and OSP. DLODP has a pH optimum of 5.5 and is inhibited by vanadate but not by NaF. Polyprenyl diphosphates inhibit [(3)H]OSP release from [(3)H]DLO, the length of their alkyl chains correlating positively with inhibition potency. The diphosphodiester GlcNAc2-PP-solanesol is hydrolyzed to yield GlcNAc2-P and inhibits [(3)H]OSP release from [(3)H]DLO more effectively than the diphosphomonoester solanesyl diphosphate. During subcellular fractionation of liver homogenates, DLODP codistributes with microsomal markers, and density gradient centrifugation revealed that the distribution of DLODP is closer to that of Golgi apparatus-situated UDP-galactose glycoprotein galactosyltransferase than those of dolichyl-P-dependent glycosyltransferases required for DLO biosynthesis in the ER. Therefore, a DLODP activity showing selectivity toward lipophilic diphosphodiesters such as DLO, and possessing properties distinct from other lipid phosphatases, is identified. Separate subcellular locations for DLODP action and DLO biosynthesis may be required to prevent uncontrolled DLO destruction.

Topics: Dolichol Phosphates; Dolichols; Endoplasmic Reticulum; Glycosylation; Golgi Apparatus; Hep G2 Cells; Humans; Liver; Oligosaccharides; Polyisoprenyl Phosphates; Pyrophosphatases

We reported an oligosaccharide diphosphodolichol (DLO) diphosphatase (DLODP) that generates dolichyl-phosphate and oligosaccharyl phosphates (OSPs) from DLO in vitro. This enzyme could underlie cytoplasmic OSP generation and promote dolichyl-phosphate recycling from truncated endoplasmic reticulum (ER)-generated DLO intermediates. However, during subcellular fractionation, DLODP distribution is closer to that of a Golgi apparatus (GA) marker than those of ER markers. Here, we examined the effect of brefeldin A (BFA), which fuses the GA with the ER on OSP metabolism. In order to increase the steady state level of truncated DLO while allowing formation of mature DLO (Glc3Man9GlcNAc2-PP-dolichol), dolichyl-P-mannose Man7GlcNAc2-PP-dolichol mannosyltransferase was partially downregulated in HepG2 cells. We show that BFA provokes GA endomannosidase trimming of Glc3Man9GlcNAc2-PP-dolichol to yield a Man8GlcNAc2-PP-dolichol structure that does not give rise to cytoplasmic Man8GlcNAc2-P. BFA also strikingly increased OSP derived from mature DLO within the endomembrane system without affecting levels of Man7GlcNAc2-PP-dolichol or cytoplasmic Man7GlcNAc2-P. The BFA-provoked increase in endomembrane-situated OSP is sensitive to nocodazole, and BFA causes partial redistribution of DLODP activity from GA- to ER-containing regions of density gradients. These findings are consistent with BFA-provoked microtubule-dependent GA-to-ER transport of a previously reported DLODP that acts to generate a novel endomembrane-situated OSP population.

Topics: Animals; Brefeldin A; CHO Cells; Cricetulus; Dolichol Phosphates; Dolichols; Endoplasmic Reticulum; Golgi Apparatus; Hep G2 Cells; Humans; Intracellular Membranes; Oligosaccharides; Phosphates

In all three domains of life, N-glycosylation begins with the assembly of glycans on phosphorylated polyisoprenoid carriers. Like eukaryotes, archaea also utilize phosphorylated dolichol for this role, yet whereas the assembled oligosaccharide is transferred to target proteins from dolichol pyrophosphate in eukaryotes, archaeal N-linked glycans characterized to date are derived from a dolichol monophosphate carrier, apart from a single example. In this study, glycan-charged dolichol phosphate from the hyperthermophile Pyrococcus furiosus was identified and structurally characterized. Normal and reverse phase liquid chromatography-electrospray ionization mass spectrometry revealed the existence of dolichol phosphate charged with the heptasaccharide recently described in in vitro studies of N-glycosylation on this species. As with other described archaeal dolichol phosphates, the α- and ω-terminal isoprene subunits of the P. furiosus lipid are saturated, in contrast to eukaryal phosphodolichols that present only a saturated α-position isoprene subunit. Interestingly, an additional 1-4 of the 12-14 isoprene subunits comprising P. furiosus dolichol phosphate are saturated, making this lipid not only the longest archaeal dolichol phosphate described to date but also the most highly saturated.

Topics: Archaea; Butadienes; Dolichol Phosphates; Dolichols; Glycosylation; Hemiterpenes; Oligosaccharides; Pentanes; Phosphate Transport Proteins; Polysaccharides; Pyrococcus furiosus

Dolichol monophosphate (Dol-P) functions as an obligate glycosyl carrier lipid in protein glycosylation reactions. Dol-P is synthesized by the successive condensation of isopentenyl diphosphate (IPP), with farnesyl diphosphate catalysed by a cis-isoprenyltransferase (cis-IPTase) activity. Despite the recognition of cis-IPTase activity 40 years ago and the molecular cloning of the human cDNA encoding the mammalian enzyme, the molecular machinery responsible for regulating this activity remains incompletely understood. Here, we identify Nogo-B receptor (NgBR) as an essential component of the Dol-P biosynthetic machinery. Loss of NgBR results in a robust deficit in cis-IPTase activity and Dol-P production, leading to diminished levels of dolichol-linked oligosaccharides and a broad reduction in protein N-glycosylation. NgBR interacts with the previously identified cis-IPTase hCIT, enhances hCIT protein stability, and promotes Dol-P production. Identification of NgBR as a component of the cis-IPTase machinery yields insights into the regulation of dolichol biosynthesis.

Topics: Alkyl and Aryl Transferases; Animals; Carrier Proteins; Chlorocebus aethiops; COS Cells; Dolichol Phosphates; Dolichols; Enzyme Activation; Glycoproteins; Humans; Protein Conformation; Receptors, Cell Surface; Vesicular Transport Proteins

The mechanism of induction of apoptosis by dolichyl phosphate (Dol-P) was investigated in U937 cells. Studies using isolated mitochondria revealed that the respiratory complex II activity was almost completely inhibited by 20 microg/ml of Dol-P but not by the same concentration of dolichol. Activities of complex I and III were also inhibited by Dol-P, but nearly 50% of activity still remained at 20 microg/ml. Dol-P induced release of cytochrome-c from the isolated mitochondria. Fluorometric microtiter plate assay revealed that generation of reactive oxygen species (ROS) increased in a time-dependent manner. Flow cytometric analysis also indicated that Dol-P caused loss of mitochondrial membrane potential (Deltapsi(m)) and increased ROS generation. The addition of the antioxidant pyrrolidine dithiocarbamate (PDTC) significantly inhibited Dol-P-induced ROS generation and activation of caspase-3. A specific inhibitor of respiratory complex II, thenoyltrifluoroacetone (TTFA), increased ROS generation, potentially mimicking the consequence of inhibition of electron flow at complex II by Dol-P in U937 cells. Electron microscopy revealed that mitochondria became swollen and spherical in shape by the treatment with Dol-P. Neither the tyrosine kinase inhibitor k252a nor mitogen activated protein kinase/extracellular signal-regulated kinase kinase (MEK) inhibitors PD98059 and U0126 inhibited the Dol-P-induced apoptosis. Together, these results suggest that the direct disruption of mitochondrial respiratory complexes and the consequent ROS generation play a critical role in the initiation of Dol-P-induced apoptosis.

Topics: Apoptosis; Benzoquinones; Caspase 3; Caspase Inhibitors; Cell Line, Tumor; Cell Respiration; Cell Shape; Cytochromes c; Dolichol Phosphates; Dolichols; Enzyme Activation; Enzyme Inhibitors; Humans; Lactams, Macrocyclic; Microscopy, Electron, Transmission; Mitochondria; Mitogen-Activated Protein Kinases; Pyrrolidines; Reactive Oxygen Species; Rifabutin; Thiocarbamates; Time Factors

Evidence is presented that temperature-sensitive Saccharomyces cerevisiae mutants, impaired in dolichol kinase (Sec59p) or dolichyl phosphate mannose synthase (Dpm1p) activity have an aberrant cell wall composition and ultrastructure. The mutants were oversensitive to Calcofluor white, an agent interacting with the cell wall chitin. In accordance with this, chemical analysis of the cell wall alkali-insoluble fraction indicated an increased amount of chitin and changes in the quantity of beta1,6- and beta1,3-glucan in sec59-1 and dpm1-6 mutants. In order to unravel the link between the formation of dolichyl phosphate and dolichyl phosphate mannose and the cell wall assembly, we screened a yeast genomic library for a multicopy suppressors of the thermosensitive phenotype. The RER2 and SRT1 genes, encoding cis-prenyltransferases, were isolated. In addition, the ROT1 gene, encoding protein involved in beta1,6-glucan synthesis (Machi et al., 2004) and protein folding (Takeuchi et al., 2006) acted as a multicopy suppressor of the temperature-sensitive phenotype of the sec59-1 mutant. The cell wall of the mutants and of mutants bearing the multicopy suppressors was analysed for carbohydrate and mannoprotein content. We also examined the glycosylation status of the plasma membrane protein Gas1p, a beta1,3-glucan elongase, and the degree of phosphorylation of the Mpk1/Slt2 protein, involved in the cell wall integrity pathway.

Topics: Cell Wall; Dolichol Phosphates; Dolichols; Gene Expression Regulation, Fungal; Glycosylation; Ligases; Mannose; Phosphotransferases (Alcohol Group Acceptor); Point Mutation; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins

The objective of these studies was to test the hypothesis that proteins that contain potential polyisoprenyl recognition sequences (PIRSs) in their transmembrane-spanning domain can bind to the polyisoprenyl (PI) glycosyl carrier lipids undecaprenyl phosphate (C55-P) and dolichyl phosphate (C95-P). A number of prokaryotic and eukaryotic glycosyltransferases that utilize PI coenzymes contain a conserved PIRS postulated to be the active PI binding domain. To study this problem, we first determined the 3D structure of a PIRS peptide, NeuE, by homonuclear 2D 1H-nuclear magnetic resonance (NMR) spectroscopy. Experimentally generated distance constraints derived from nuclear Overhauser enhancement and torsion angle constraints derived from coupling constants were used for restrained molecular dynamics and energy minimization calculations. Molecular models of the NeuE peptide were built based on calculations of energy minimization using the DGII program NMRchitect. 3D models of dolichol (C95) and C95-P were built based on our 2D 1H-NMR nuclear Overhauser enhancement spectroscopy (NOESY) results and refined by energy minimization with respect to all atoms using the AMBER (assisted modeling with energy refinements) force field. Our energy minimization studies were carried out on a conformational model of dolichol that was originally derived from small-angle X-ray scattering and molecular mechanics methods. These results revealed that the PIs are conformationally nearly identical tripartite molecules, with their three domains arranged in a coiled, helical structure. Analyses of the intermolecular cross-peaks in the 2D NOESY spectra of PIRS peptides in the presence of PIs confirmed a highly specific interaction and identified key contact amino acids in the NeuE peptide that constituted a binding motif for interacting with the PIs. These studies also showed that subtle conformational changes occurred within both the PIs and the NeuE peptide after binding. 3D structures of the resulting molecular complexes revealed that each PI could bind more than one PIRS peptide. These studies thus represent the first evidence for a direct physical interaction between specific contact amino acids in the PIRS peptides and the PIs and supports the hypothesis of a bifunctional role for the PIs. The central idea is that these superlipids may serve as a structural scaffold to organize and stabilize in functional domains PIRS-containing proteins within multiglycosyltransferase complexes

Topics: Amino Acid Sequence; Bacterial Proteins; Binding Sites; Computer Simulation; Dolichol Phosphates; Dolichols; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Sequence Data; Oligopeptides; Polyisoprenyl Phosphates; Protein Binding; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Proteins

The effects of two peroxisome proliferators, gemfibrozil and clofibrate, on syntheses of dolichol and cholesterol in rat liver were investigated. Gemfibrozil did not affect the overall content of dolichyl phosphate, but it changed the chain-length distribution of dolichyl phosphate, increasing the levels of species with shorter isoprene units. Gemfibrozil suppressed synthesis of dolichyl phosphate from [(3)H]mevalonate and [(3)H]farnesyl pyrophosphate in rat liver. In contrast, clofibrate increased the content of dolichol (free and acyl ester forms). It remarkably enhanced dolichol synthesis from mevalonate, but did not affect dolichol synthesis from farnesyl pyrophosphate. Gemfibrozil elevated cholesterol synthesis from [(14)C]acetate, but did not affect the synthesis from mevalonate. Clofibrate suppressed cholesterol synthesis from acetate, but did not affect cholesterol synthesis from mevalonate. These results suggest that gemfibrozil suppresses synthesis of dolichyl phosphate by inhibiting, at the least, the pathway from farnesyl pyrophosphate to dolichyl phosphate. As a result, the chain-length pattern of dolichyl phosphate may show an increase in shorter isoprene units. Clofibrate may increase the content of dolichol by enhancing dolichol synthesis from mevalonate. Gemfibrozil may increase cholesterol synthesis by activating the pathway from acetate to mevalonate. Unlike gemfibrozil, clofibrate may decrease cholesterol synthesis by inhibiting the pathway from acetate to mevalonate.

Topics: Acetates; Animals; Carbon Radioisotopes; Cholesterol; Clofibrate; Dolichol Phosphates; Dolichols; Gemfibrozil; Liver; Male; Mevalonic Acid; Peroxisome Proliferators; Polyisoprenyl Phosphates; Rats; Rats, Wistar; Sesquiterpenes; Tritium

The control of ubiquinone biosynthesis by peroxisome proliferators was investigated using peroxisome proliferator activated receptor alpha (PPARalpha)-null mice. Administration of 2-(diethylhexyl)phthalate to control mice resulted in elevated ubiquinone levels in the liver, while dolichol, dolichyl-P and cholesterol concentrations remained unchanged. In PPARalpha-null mice, the level of these lipids were similar to control levels and administration of the peroxisome proliferator did not increase the levels of ubiquinone. The increase in ubiquinone levels was the result of increased synthesis. Induction was most pronounced in liver, kidney and heart, which have relatively high levels of PPARalpha. When the tissue concentration of hydrogen peroxide was elevated by inhibition of catalase activity with aminotriazole, the amount of ubiquinone was not increased, suggesting that the induction of ubiquinone synthesis occured through a direct mechanism. The activities of branch-point enzymes FPP-synthase, squalene synthase, cis-prenyltransferase, trans-prenyltransferase and NPHB-transferase were substantially increased in control but not in PPARalpha-null mice after treatment with peroxisome proliferators. These data suggest that the induction of ubiquinone biosynthesis after administration of peroxisome proliferators is dependent on the PPARalpha through regulation of some of the mevalonate pathway enzymes.

Topics: Alkyl and Aryl Transferases; Animals; Catalase; Cholesterol; Diethylhexyl Phthalate; Dolichol Phosphates; Dolichols; Enzyme Induction; Farnesyl-Diphosphate Farnesyltransferase; Gene Deletion; Half-Life; Hydrogen Peroxide; Liver; Male; Mevalonic Acid; Mice; Mice, Inbred Strains; Mice, Knockout; Organ Specificity; Receptors, Cytoplasmic and Nuclear; Transcription Factors; Ubiquinone

The biosynthesis of cholesterol, dolichol and dolichyl-P were investigated in a murine model of Niemann-Pick type C disease using both in vitro and in vivo systems. In vivo incorporation of [3H]mevalonate into squalene, dolichol and dolichyl-P decreased. The amount of dolichyl-P was elevated due to a decrease in the rate of degradation. Labeling of squalene and cholesterol of liver homogenates in vitro was decreased in the diseased mice and a lowering of microsomal activities of both HMG-CoA reductase and squalene synthase were also observed. In experiments with brain homogenate, decreased [3H]mevalonate labeling of squalene, cholesterol and dolichol was found in vitro. The decreases in cis-prenyltransferase and squalene synthase activities were observed at a very early phase of the disease. In contrast to the decreased biosynthesis of cholesterol observed in vitro, the labeling of total liver cholesterol was found to be increased in Niemann-Pick type C liver upon in vivo investigation, possibly due to the accumulation of this lipid as a result of a deficient transport process. In the brain, where in vivo labeling reflects only biosynthesis, a decreased rate of cholesterol synthesis was demonstrated.

Topics: Animals; Brain; Cholesterol; Disease Models, Animal; Dolichol Phosphates; Dolichols; Farnesyl-Diphosphate Farnesyltransferase; Hydroxymethylglutaryl CoA Reductases; Liver; Male; Mevalonic Acid; Mice; Mice, Inbred BALB C; Microsomes, Liver; Niemann-Pick Diseases; Squalene; Transferases; Tritium

Previous studies have demonstrated that acute ethanol intoxication affects various steps of protein glycosylation at the level of rat liver endoplasmic reticulum and Golgi apparatus. The aim of this investigation was to demonstrate whether chronic ethanol intake can induce definitive changes of liver glycoprotein processing. Rats were given ethanol by liquid diet for 8 weeks. At the end of this period the triglyceride levels in liver homogenate and microsomes were significantly higher than in controls. Isolated hepatocytes prelabelled with [3H]Na palmitate and [14C]glucosamine showed a significant storage of the lipid and carbohydrate radioactivity in microsomes and Golgi apparatus and a significant impairment of labelled glycolipoprotein secretion. Changes of the glycosylation steps were observed both in endoplasmic reticulum and in Golgi apparatus: in the former the levels of dolichyl phosphate, which is rate-limiting for the synthesis of glycoprotein, showed a significant reduction; in the latter the activity of the main enzymes responsible for the terminal glycosylation process was significantly decreased. These data suggest that an impairment of glycoprotein maturation may be involved in the pathogenesis of liver injury induced by chronic ethanol intake.

Topics: Alcoholism; Animals; Dolichol Phosphates; Dolichols; Ethanol; Fatty Liver, Alcoholic; Female; Glucosamine; Glycoproteins; Golgi Apparatus; Liver; Membrane Glycoproteins; Microsomes, Liver; Palmitic Acid; Palmitic Acids; Rats; Rats, Sprague-Dawley; Triglycerides

Exposure of rat glioma C6 cells to dolichyl phosphate resulted in cell shrinkage followed by nuclear fragmentation and internucleosomal cleavage of genomic DNA, yielding ladder patterns of oligonucleosomal fragments, all characteristics of apoptosis. This phenomenon occurred in a dose and time dependent manner. Dolichol and prenol failed to induce apoptosis. The inhibitors of N-glycosylation, tunicamycin and swainsonine had no apparent effect on dolichyl phosphate-induced apoptosis. Apoptotic changes were also observed in HL-60 cells, SIRC cells and HeLa cells. Thus, dolichyl phosphate functions as a potential apoptosis inducer as well as an essential carrier lipid in the biosynthesis of N-linked glycoprotein.

Topics: Animals; Apoptosis; DNA; Dolichol Phosphates; Dolichols; Electrophoresis, Agar Gel; Glioma; Glycoproteins; Glycosylation; HeLa Cells; Hemiterpenes; Humans; Kinetics; Pentanols; Rats; Swainsonine; Tumor Cells, Cultured; Tunicamycin

The distributions of mevalonate pathway lipids in various organs of a mouse strain used as a model for Niemann-Pick's type C disease were analyzed. Extensive accumulation of cholesterol was observed in all tissues with the exception of the brain, where the content of this lipid was decreased. The changes in total dolichol contents of most organs varied from a 50% decrease in the lung to a twofold increase in kidney and heart. There was relative enrichment of longer-chain dolichols, but no increase in the relative amount of alpha-unsaturated polyprenols was observed. The levels of dolichyl phosphate in all organs were increased, and most of this lipid was associated with bound oligosaccharides or proteins. Ubiquinone levels were largely unchanged. Subfractionation studies revealed that heavy and light lysosomes exhibited a 10-fold increase in cholesterol level, the amount of dolichol was decreased in lysosomes and increased in microsomes, and there was an increase in the dolichyl phosphate levels of all three of these subfractions. These results indicate that in diseased mice cholesterol accumulation in various organs is paralleled by an increase in the dolichyl phosphate concentration, whereas dolichol transport from the endoplasmic reticulum to lysosomes is inhibited.

Topics: Animals; Cholesterol; Dolichol Phosphates; Dolichols; Mevalonic Acid; Mice; Mice, Inbred BALB C; Microscopy, Electron; Niemann-Pick Diseases; Subcellular Fractions; Tissue Distribution; Ubiquinone

Rat intoxication with a single dose of 1,2-dichloroethane (DCE) (50 microliters/100 g b.w) is able to induce a significant modification of protein glycosylation in the liver endoplasmic reticulum and Golgi apparatus. HPLC analysis shows that within 5-60 min after DCE-intoxication, the levels of total dolichol, free dolichol and dolichyl phosphate strongly decreased in the microsomes and Golgi apparatus. Particularly in total microsomes, dolichyl phosphate, which is rate-limiting for the biosynthesis of the N-linked oligosaccharide chains, drops to values significantly lower than in the control group 15 min after DCE poisoning. In the Golgi apparatus, the total dolichol, essential to enhance the fluidity and permeability of these membranes, early and significantly decreases already 5 min after DCE poisoning. Moreover, in the Golgi apparatus galactosyl- and sialyltransferase activities, the main enzymatic activities of terminal protein glycosylation, are significantly reduced, as measured 15 min after DCE intoxication. These data suggest that the impairment of glycoprotein synthesis, maturation and secretion may be involved in the pathogenesis of liver injury induced by acute DCE-intoxication.

Topics: Alanine Transaminase; Animals; Aspartate Aminotransferases; Cell Membrane Permeability; Chromatography, High Pressure Liquid; Dolichol Phosphates; Dolichols; Endoplasmic Reticulum; Ethylene Dichlorides; Galactosyltransferases; Glycosylation; Glycosyltransferases; Golgi Apparatus; Liver; Male; Membrane Fluidity; Microsomes, Liver; Rats; Sialyltransferases; Triglycerides

The levels and rates of biosynthesis of mevalonate pathway lipids in rat brain were investigated during development and aging. Between birth and 18 months of age there are only moderate decreases in the phospholipid and cholesterol contents but an increase in the levels of dolichyl-P and, particularly of dolichol. The amount of ubiquinone is unchanged. The rate of incorporation of [3H]leucine into protein decreases by 10% during the first year, while the incorporation of [3H]glycerol into phospholipids decreases by 20%. The high rates of [3H]mevalonate incorporation into cholesterol and dolichol after birth decreases rapidly. In contrast, the rate of incorporation into ubiquinone is constant. Squalene synthase activity decreases rapidly in the early postnatal period and at 18 months of age this activity is 10-fold lower than immediately after birth. cis-Prenyltransferase activity is also high during the first postnatal month and reaches a constant level at 4 months of age. Significantly, nonaprenyl 4-hydroxybenzoate transferase activity is high during the entire period investigated. The rate of lipid peroxidation does not change during aging. These results demonstrate that brain cholesterol and dolichol exhibit a low rate of turnover during aging, whereas ubiquinone is synthesized at a high rate and exhibits rapid turnover throughout the entire lifespan.

Topics: Aging; Alkyl and Aryl Transferases; Animals; Animals, Newborn; Brain; Cholesterol; Dolichol Phosphates; Dolichols; Farnesyl-Diphosphate Farnesyltransferase; In Vitro Techniques; Lipid Metabolism; Male; Mevalonic Acid; Phospholipids; Rats; Rats, Sprague-Dawley; Transferases

Sequential microanalyses of free dolichol, dolichyl fatty acid ester and dolichyl phosphate in human serum were made. To determine the level of each dolichol, samples were pretreated using three different methods prior to fluorescent derivatization. To estimate the concentrations of free dolichol, samples were added to alkaline methanol and kept at room temperature for 1 h. In case of dolichyl fatty acid ester, samples were saponified at 100 degrees C for 1 h. To estimate dolichyl phosphate, saponified lipid extracts were treated with acid phosphatase. Each pretreated dolichol was reacted with anthracene-9-carboxylic acid and amounts of 9-anthroyl derivatives were determined fluorometrically by HPLC. This method is simple and three types of dolichols can be estimated using the same HPLC system. This analysis is also sufficiently sensitive for measurement of serum dolichol levels. The contents of free dolichol, dolichyl fatty acid ester and dolichyl phosphate in human serum were found to be 44.9 +/- 10.5 ng/ml (n = 32), 76.4 +/- 24.2 ng/ml (n = 32) and 43.5 +/- 15.1 ng/ml (n = 13), respectively. These levels had apparently no correlation to age or serum total cholesterols. A linear correlation between dolichols and high-density lipoprotein cholesterols reflects the fact that the dolichols are associated with the high-density lipoprotein fraction.

Topics: Chromatography, High Pressure Liquid; Dolichol Phosphates; Dolichols; Esters; Humans; Lipoproteins, HDL

Inhibitors of hydroxymethylglutaryl coenzyme A reductase are used clinically to decrease blood levels of low-density lipoprotein cholesterol in hypercholesterolemic patients. However, little is known about the possible effects of these inhibitors on dolichol and cholesterol synthesis. Oral administration of mevinolin to rats was found here to decrease dolichol, dolichyl-P and coenzyme Q levels in the heart and skeletal muscle and to increase the hepatic dolichol level while decreasing the coenzyme Q content in this same organ. The amounts of dolichyl-P decreased in heart and muscle and increased in brain. Intraperitoneal administration also affected the levels of these lipids. The concentrations of blood lipids were not modified in the same manner as tissue lipids. Analysis of individual enzyme activities and of incorporation of [3H]acetate into various lipids of liver and brain slices demonstrated that both up- and down-regulation of different proteins occur in various tissues, resulting in modifications in lipid synthesis. Hypercholesterolemic patients were found to have high blood coenzyme Q levels, which are decreased upon pravastatin treatment, although they are still above control values. It appears that these HMG-coenzyme A reductase inhibitors do not selectively lower cholesterol levels, but that they also modify the dolichol and coenzyme Q content and synthesis both in the liver and various other tissues.

Topics: Animals; Dolichol Phosphates; Dolichols; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; In Vitro Techniques; Pravastatin; Rats; Ubiquinone

The relative contribution of the Sertoli cell and the pachytene spermatocyte to dolichol and N-linked oligosaccharide biosynthesis within the seminiferous tubule was investigated. Evidence is presented to show that the interaction between these two cell types affects dolichol and N-linked oligosaccharide biosynthesis. Analysis of the dolichol content of Sertoli cultures confirms earlier data suggesting that the Sertoli cell constitutes the major pool of dolichols within the seminiferous tubule. [14C]Acetate incorporation studies suggest that the Sertoli cell in culture synthesizes dolichol much more rapidly than does the isolated pachytene spermatocyte. This information, in addition to previous data in the literature, infers an interactive effect whereby the presence of the spermatogenic cell in the tubule stimulates dolichol synthesis in the Sertoli cell. The absence of normal Sertoli-spermatocyte interactions in in vitro incubations may also limit dolichol synthesis in the pachytene spermatocyte. The distribution of dolichol kinase between the Sertoli and the pachytene spermatocyte was also examined. The concentration of this enzyme in the Sertoli cell suggests the presence of an active salvage pathway within that cell. The correlation between the appearance of the pachytene spermatocyte and the previously described peak of dolichol kinase activity in the seminiferous tubules of the prepubertal animal implies cell-cell interactions. Radiolabelling studies of N-linked oligosaccharides were conducted using [3H]mannose and concanavalin A affinity chromatography to identify multiantennary, biantennary, and high-mannose oligosaccharide pools. An in vitro bicameral coculture system was used to demonstrate that pachytene spermatocytes stimulate incorporation of [3H]mannose into Sertoli cell oligosaccharides.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Cell Communication; Dolichol Phosphates; Dolichols; Glycopeptides; Male; Oligosaccharides; Phosphotransferases; Phosphotransferases (Alcohol Group Acceptor); Rats; Rats, Sprague-Dawley; Seminiferous Tubules; Sertoli Cells; Spermatocytes; Testis

Rats were treated with mevinolin by intraperitoneal injection (15 days) or dietary administration (30 days). The cholesterol, dolichol, dolichyl phosphate and ubiquinone contents of the liver, brain, heart, muscle and blood were then investigated. The cholesterol contents of these organs did not change significantly, with the exception of muscle. Intraperitoneal administration of the drug increases the amount of dolichol in liver, muscle and blood and decreases the dolichyl-P amount in muscle. The same treatment increases the level of ubiquinone in muscle and blood and decreases this value in liver and heart. Oral administration decreases dolichol, dolichyl-P and ubiquinone levels in heart and muscle, while in liver the dolichol level is elevated and ubiquinone level lowered. In brain the amount of dolichyl-P is increased. Intraperitoneal injection of mevinolin also modifies the liver dolichol and dolichyl-P isoprenoid pattern, with an increase in shorter chain polyisoprenes. The levels of dolichol and ubiquinone in the blood do not follow the changes observed in other tissues. Incorporation of [3H]acetate into cholesterol by liver slices prepared from mevinolin-treated rats exhibited an increase, whereas in brain no change was seen. Labeling of dolichol and ubiquinone was increased in both liver and brain, but incorporation into dolichyl phosphate remained relatively stable. The results indicate that mevinolin affects not only HMG-CoA reductase but, to some extent, also affects certain of the peripheral enzymes, resulting in considerable effects on the various mevalonate pathway lipids.

Topics: Acetates; Animals; Cholesterol; Dolichol Phosphates; Dolichols; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Lipid Metabolism; Liver; Lovastatin; Male; Organ Specificity; Rats; Rats, Sprague-Dawley; Ubiquinone

Dolichyl phosphate, dolichol C80-105 (dolichol 17:dihydroheptadecaprenol-dolichol 21:dihydrohexeicosaprenol), and dolichol C55 (dolichol 11:dihydroundecaprenol) were separated by anion-exchange paper chromatography. Squalene, sterols, phospholipids, anionic glycolipids, and glycerol did not migrate as dolichyl phosphate, dolichol C80-105, and dolichol C55 under our elution conditions. However, since the Rf of triglycerides was similar to that of dolichol C80-105, saponification, prior to chromatography, removed traces of triglycerides. Silica gel thin-layer chromatography (TLC) allowed the separation of dolichol C80-105 from dolichol C55, whereas dolichyl phosphate was eluted with other lipids. Incubation of spontaneously transformed cells derived from rat astrocytes primary cultures with [2-14C]acetate, saponification of the extracted lipids, and anion-exchange paper chromatography revealed the presence of radioactive dolichyl phosphate and dolichol C80-105 (15 pmol/mg protein). Extraction of labeled dolichyl phosphate followed by acid phosphatase treatment and subsequent analysis on TLC confirmed the identity of dolichyl phosphate since all the radioactivity was associated with dolichol C55. Treatment of the transformed cells with 30 microM 7-ketocholesterol or 7 beta-hydroxycholesterol stimulated markedly (two- to threefold) the incorporation of [2-14C]-acetate in both dolichol C80-105 and dolichyl phosphate. These data demonstrate that anion-exchange paper chromatography is technically suitable for the separation and analysis of dolichol C55, dolichol C80-105, and dolichyl phosphate in cultured cells prelabeled with radioactive precursors.

Topics: Acetates; Animals; Animals, Newborn; Astrocytes; Brain; Brain Chemistry; Cell Death; Cell Line, Transformed; Cells, Cultured; Chromatography, Ion Exchange; Chromatography, Paper; Chromatography, Thin Layer; Dolichol Phosphates; Dolichols; Hydroxycholesterols; Ketocholesterols; Rats

The lipid compositions of various regions of the human brain were investigated during aging and in Alzheimer's disease. The phospholipid amounts and compositions remained unchanged during aging. There were, however, considerable differences both in phospholipid composition and amount when the various regions were compared. The level of dolichol increased severalfold in all regions up to the age of 70, but there was no further elevation thereafter. The ubiquinone level decreased significantly in all parts of the brain upon aging. In Alzheimer's disease, the dolichol level was decreased in all regions, and particularly, in those affected by the disease. In contrast, the dolichyl-P concentration increased in those regions that exhibited morphological changes. There was no modification in cholesterol distribution, but a significant elevation in ubiquinone content was observed in most regions. The only phospholipid whose level was elevated was phosphatidylinositol, and only in those parts of the brain that were affected. The content of polyunsaturated fatty acids in phosphatidylethanolamine was greatly decreased in connection with the disease, with a parallel increase in the saturated portion. The results indicate that Alzheimer's disease results in specific and significant changes in the levels of lipid products of the mevalonate pathway in the brain.

Topics: Aged; Aging; Alzheimer Disease; Brain Chemistry; Cholesterol; Dolichol Phosphates; Dolichols; Fatty Acids; Humans; Membrane Lipids; Mevalonic Acid; Middle Aged; Phosphatidylinositols; Phospholipids; Ubiquinone

The concentrations of the three major cellular forms of dolichol (free, esterified and phosphorylated) were determined in murine liver, kidney and heart. The tissue levels of these forms of dolichol were studied in detail as a function of age. Changes in the activities of dolichyl phosphate phosphatase and dolichol kinase were also determined. In liver, the concentration of unesterified dolichol, fatty acyl dolichol and dolichyl phosphate increased markedly over a period of 6 to 25 months (four-fold, 5.5-fold and nine-fold, respectively). In kidney only, free dolichol and phosphorylated dolichol increased (approximately four-fold in each case). However, this tissue consistently showed the highest concentrations of all forms of dolichol as compared to liver and heart. In heart, both free and esterified dolichol concentrations increased (approximately 3.25-fold in each case); dolichyl phosphate levels were not determined in this tissue. In all tissues studied, the activity of the dolichyl phosphate phosphatase enzyme was considerably higher than that of the dolichol kinase enzyme. In liver, there was no evidence to suggest that either enzyme was critical in determining the relative concentrations of dolichol and dolichyl phosphate. Evidence for such a role for the kinase in the kidney was stronger. Treatment of aging mice with meclofenoxate, a drug that is reported to cause dissolution of lipofuscin, failed to prevent accumulation of dolichol and dolichyl phosphate with age. These observations suggest that not all accumulated dolichol is associated with lipofuscin. Meclofenoxate treatment had no consistent effect on the activities of the enzymes studied.

Topics: Aging; Animals; Body Weight; Dolichol Phosphates; Dolichols; Female; Heart; Kidney; Lipofuscin; Liver; Male; Meclofenoxate; Mice; Myocardium; Organ Size; Phosphoric Monoester Hydrolases; Phosphotransferases; Phosphotransferases (Alcohol Group Acceptor)

Carbon tetrachloride (CCl4) poisoning affects glycoprotein processing and maturation at the level of rat liver microsomes and Golgi apparatus. HPLC analysis showed that within 5-60 min after CCl4 administration the levels of total dolichol, free dolichol and dolichyl-phosphate strongly decreased both in total microsomes and in Golgi apparatus. The most marked and early reduction of total dolichol was observed in the secretory membranes of Golgi area already 15 min after CCl4 poisoning. The incubation of CCl4-pretreated isolated hepatocytes with [3H]-mevalonate showed a significant slowing down of the label incorporation into both free-dolichol and dolichyl-phosphate. Moreover, lipid peroxidation might cause alterations in the molecular structure of both free-dolichol and dolichyl-phosphate. A notable prevention of dolichol decrease was observed in animals pretreated with vitamin E. The results suggest that the prooxidant activity of CCl4 is able to affect the metabolism of dolichol either by increasing the oxidative degradation or impairing the biosynthetic pathway.

Topics: Animals; Carbon Tetrachloride Poisoning; Dolichol Phosphates; Dolichols; Golgi Apparatus; Kinetics; Lipid Peroxidation; Liver; Male; Mevalonic Acid; Microsomes, Liver; Oxidation-Reduction; Rats; Rats, Inbred Strains; Vitamin E

Surgical samples of human hepatic tissue were analysed morphologically and biochemically and highly differentiated hepatomas were compared with two control groups: morphologically normal liver tissue surrounding the tumour, and tissue from normal livers. In tumour homogenates cholesterol levels were more than twice, ubiquinone levels about half and the concentration of free dolichol about 10% of the control value. The levels of dolichyl phosphate were basically similar, whereas the phospholipid level was slightly lower in the tumours. In microsomes isolated from hepatomas, the level of cholesterol was about 30% higher than the control value. HMG-CoA reductase activity in microsomes isolated from hepatomas was elevated almost 100% in comparison to control. In hepatomas, no major alterations in the compositions of dolichol or dolichyl phosphate could be observed. The relative amounts of alpha-saturated and alpha-unsaturated polyprenols were also basically unaltered in hepatomas. Liver samples were incubated with 3H-mevalonic acid and radioactivity was monitored in polyprenols. With control tissue, incorporation was considerably higher in alpha-unsaturated polyprenols than in their alpha-saturated counterparts. In the tumours the rates of incorporation into both polyprenol fractions were much lower, although still higher in the alpha-unsaturated fraction. Labelling of polyisoprenols containing 19 isoprene residues was higher than that of 20 residues. The pattern of labelling in the polyisoprenyl-P fraction was similar. In hepatomas the incorporation into cholesterol and ubiquinone-10 was about 100% higher and 50% lower respectively compared with control tissue. The results in this study of hepatomas indicate that the levels of various lipids may be influenced not only by the regulatory enzyme HMG-CoA reductase, but also by other enzymes catalysing reactions subsequent to this regulatory point. It is also suggested that levels of cholesterol, ubiquinone and dolichol may be regulated independently subsequent to the branch point at farnesylpyrophosphate.

Topics: Carcinoma, Hepatocellular; Cholesterol; Dolichol Phosphates; Dolichols; Humans; Liver Neoplasms; Terpenes; Ubiquinone

The content and the percent distribution of dolichol and dolichyl phosphate homologues were measured by high-performance liquid chromatography in perinatal rat livers. Short dolichol chains and no dolichyl phosphate are detectable in the liver at foetal stages; dolichol content progressively increases during liver development. A good correlation is observable between the changes of the dolichol, dolichyl phosphate and the activity of dolichyl-phosphate phosphatase.

Topics: Animals; Chromatography, High Pressure Liquid; Dolichol Phosphates; Dolichols; Gestational Age; Liver; Phosphoric Monoester Hydrolases; Phosphorylation; Rats; Rats, Inbred Strains

The age-associated changes in the levels and synthesis of dolichyl phosphate and dolichyl diphosphate derivatives were investigated in brain and liver of 057B1/NNia mice. The total chloroform/methanol (2:1, v/v)-extractable phosphorylated dolichols of brain increased from 1.01 micrograms/g at 3 months to 5.22 micrograms/g at 28 months of age. The long-chain dolichyl diphosphate oligosaccharide (Dol-PP-oligo) levels of brain increased from 0.82 microgram/g in 3 months to 2.8 micrograms/g in 28-month-old animals. However, in liver and in kidney, the levels of these components were unaffected by age. Incorporation of labelled glucose from UDP-glucose into dolichyl phosphate glucose and Dol-PP-oligo in brain microsomes was unaffected by age, whereas, in liver microsomes, the rates of synthesis of both components increased by 50-150%. The increased rate of synthesis and lack of accumulation of Dol-PP-oligo in liver suggest an active utilization and/or catabolism of these glycoprotein precursors. The accumulation of Dol-PP-oligo in aging brain may reflect its decreased utilization for N-glycosylation and/or reduced catabolism.

Topics: Aging; Animals; Brain; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Dolichol Phosphates; Dolichols; Glycoproteins; Mice; Mice, Inbred C57BL; Microsomes; Microsomes, Liver; Phosphorylation; Spectrophotometry, Ultraviolet

An effective system for perfusing rat liver using complete tissue culture medium and washed calf erythrocytes as oxygen carriers was devised. Infusion of taurocholate and glucose proved necessary to maintain stable metabolic activity and bile secretion during a 6-hr period. Perfusate pO2, pCO2 and pH values were monitored continuously and found to be stable. Electron microscopic examination revealed the maintenance of normal hepatic structure, even after 6 hr. Normal rates of protein and urea synthesis, no leakage of cytoplasmic enzymes, and continuous bile acid production demonstrated the functional integrity of this system. Using [3H]mevalonic acid as precursor, dolichol, dolichyl phosphate, ubiquinone and cholesterol were found to be continuously synthesized in this perfused liver system. All these lipids appeared in the perfusate, indicating discharge through the ER-Golgi system. The lipoproteins of the perfusate were isolated by ultracentrifugation and characterized with respect to size distribution and lipid composition. Dolichol was found in VLDL, LDL and HDL fractions, with the highest concentration present in the latter. In rat and human blood plasma this lipid was mainly associated with HDL. The ubiquinone in the perfusate was primarily associated with the VLDL fraction, while in rat plasma it was found more evenly distributed among all the three lipoprotein fractions studied. Dolichol, ubiquinone and cholesterol were also discharged to the bile, whereas dolichyl phosphate was not. Thus, newly-synthesized dolichol and ubiquinone are transported out of the hepatocyte to the blood and to the bile.

Topics: Animals; Bile; Dolichol Phosphates; Dolichols; In Vitro Techniques; Lipoproteins; Liver; Male; Microscopy, Electron; Perfusion; Rats; Rats, Inbred Strains; Ubiquinone

The total amounts of cholesterol, dolichol and dolichyl phosphate (Dol-P) in kidneys and liver from 1- and 24-month-old mice were measured after saponification of the tissues. The cholesterol content of kidneys decreased by about 4-fold per g of tissue between the two ages, while the amount of cholesterol/g liver remained constant. The dolichol content of both tissues increased by about 2-fold. The amount of Dol-P in kidneys increased by 7-fold over 23 months, while the concentration in liver decreased some 6-fold. Metabolic labelling experiments using tritiated water demonstrated that the rate of synthesis of total dolichol (dolichol + Dol-P) in the kidneys did not change as a function of age. However, the kidneys of young mice incorporated 3-fold more radioactivity into dolichol than Dol-P, whereas this distribution was reversed in old mice. In liver, the rate of dolichol synthesis decreased 2-fold over 23 months. It was not possible to compare the rates of Dol-P biosynthesis between ages as Dol-P was undetectable in liver of old mice. The relative abundance of the 19 isoprene unit homologs of both dolichol and Dol-P decreased approx. 5% while the 17 isoprene unit homologs increased by a similar amount in both tissues of the old mice.

Topics: Aging; Animals; Cholesterol; Chromatography, High Pressure Liquid; Dolichol Phosphates; Dolichols; Kidney; Liver; Male; Mice; Mice, Inbred CBA; Phosphorus Radioisotopes; Polyisoprenyl Phosphates; Tritium

The aim of the present report was to analyze the pattern of glycoprotein synthesis in rat liver on 19th and 22nd day of pregnancy by following the incorporation of 14C-glucosamine and 3H-galactose into isolated rat hepatocytes, the N-acetylglucosaminyl-1-P and galactosyl transferase activities, and the liver content of dolichol and dolichyl-phosphate. The data obtained show a decrease of precursor incorporation into glycoproteins during the last period of pregnancy; this decrease is independent of enzyme activities. The dolichol content increases and the dolichyl-phosphate content, usually considered as rate limiting for glycosylation, decreases. These results, present in other conditions of proliferation and differentiation of rat liver, could explain the differences in membrane organization, the increase of hepatic proteolysis and the alteration in secretory activity during the last phase of gestation.

Topics: Animals; Dolichol Phosphates; Dolichols; Female; Galactose; Glucosamine; Glycoproteins; Glycosylation; Liver; Pregnancy; Pregnancy, Animal; Rats; Rats, Inbred Strains

Homogenates and microsomal fractions prepared from biopsies of highly differentiated human hepatocellular carcinomas were found to contain low levels of dolichol in comparison with control tissue. In contrast, the amount of dolichyl phosphate in tumor homogenates was unchanged and actually increased in the microsomal fraction. The pattern of individual polyisoprenoids, both in the free and the phosphorylated dolichol fractions of hepatomas, did not exhibit any major alterations compared to the control. The rates of incorporation of [3H]mevalonic acid into dolichol and dolichyl phosphate in hepatomas were low. The dolichol monophosphatase activities in microsomal fractions from hepatomas and controls did not show any major differences, whereas the activity of the CTP-dependent dolichol kinase was increased in tumor microsomes. Glycosylation of endogenous dolichyl phosphate and of total protein using certain nucleotide-activated sugars was found to be slightly elevated in microsomal fractions from the tumor itself when compared to the control. The reasons for the differences in the levels of polyisoprenoids in hepatomas and control tissue are discussed.

Topics: Carcinoma, Hepatocellular; Cytidine Triphosphate; Cytosine Nucleotides; Dolichol Phosphates; Dolichols; Glycosylation; Humans; Liver Neoplasms; Mevalonic Acid; Microsomes, Liver; Middle Aged; Phosphoric Monoester Hydrolases; Phosphotransferases; Phosphotransferases (Alcohol Group Acceptor); Polyisoprenyl Phosphates

Rat liver dolichol and dolichyl-P were labeled by injection of [3H]mevalonate into the portal vein and their rates of synthesis and breakdown determined. In the initial phase the radioactivity appeared in alpha-unsaturated polyprenols. Subsequent saturation required 90 min. The half-lives of dolichols in microsomes were between 80 and 118 h, and shorter dolichols had shorter values of T1/2. The half-lives of dolichols in lysosomes were between 115 and 137 h, while microsomal dolichyl-P exhibited a T1/2 of 32 h. Injected dolichol was recovered in the lysosomes of hepatocytes and exhibited a rate of breakdown which was slower than that of the endogenous compound. These results indicate differences in the catabolism of dolichol at different subcellular locations, as well as differences between the catabolism of dolichol and dolichyl-P.

Topics: Animals; Diterpenes; Dolichol Phosphates; Dolichols; Half-Life; Liver; Lysosomes; Male; Mevalonic Acid; Microsomes, Liver; Polyisoprenyl Phosphates; Rats; Rats, Inbred Strains; Terpenes

Optimal conditions for the quantitative estimation of dolichol in human plasma were determined. Because of the large amounts of other lipids present in the blood, the extraction procedure, the procedure for hydrolysis, and the HPLC procedure are of decisive importance. Human plasma contains dolichol, dolichyl esters, and dolichyl phosphate at concentrations of 41, 102, and 55 ng/g, respectively. These polyisoprenoid lipids are associated with the high density lipoprotein fraction. The relative amounts and compositions of dolichyl esters in the plasma are similar to those observed in isolated human liver microsomes and Golgi vesicles. Sixty percent of the fatty acids present are saturated and almost no long-chain polyunsaturated components are present. There is no correlation between blood dolichol content and weight, sex, dietary state, or plasma cholesterol level, but there is an inverse relationship to plasma triglyceride content. A linear increase in the total plasma dolichol content with increasing age was found. In a few pathological conditions where the level of blood cholesterol was increased, the total blood dolichol content was not affected. Apparently, dolichol is a stable lipid component of human high density lipoprotein.

Topics: Animals; Chromatography, High Pressure Liquid; Dolichol Phosphates; Dolichols; Esters; Fatty Acids; Humans; Lipoproteins; Rabbits; Rats

1. The liver of female frogs shows a significantly higher dolichol content in May (134 micrograms/g) than in November (90 micrograms/g). The male frog liver (134 micrograms/g May; 119 micrograms/g November) does not show any significant change. 2. The rat liver does not show any significant change in dolichol content from May to November (30 micrograms/g). 3. The dolichyl-phosphate level was the same in male and female frog livers and in the rat liver. 4. Data is given of the distribution of dolichols according to the number of their isoprene residues.

Topics: Animals; Dolichol Phosphates; Dolichols; Female; Liver; Male; Rana esculenta; Rats; Rats, Inbred Strains; Seasons; Species Specificity

Incubations of 10,000 X g supernatant from rat liver with [3H]mevalonate were performed and the labeling of polyprenols was studied. It was demonstrated that factors like pH, substrate concentration, and presence of detergent not only greatly influence the total incorporation but also the relative distribution of radioactivity among the isoprenologues. The synthesis was shown to be extremely sensitive to Triton X-100. Substrate concentrations of 1 and 100 microM mostly gave polyprenols with 18 and 20 isoprenes, respectively. At a given substrate concentration, pH 6.5 resulted in shorter polyprenols than did pH 7.5. Ozonolytic fragmentation demonstrated that in the initial phase of incubation, polyprenols are elongated by 1 isoprene residue and saturated to give dolichols. No substantial dephosphorylation of polyprenyl phosphates to the free alcohol occurred. The production of dolichol in vitro was shown to utilize NADH for the saturation event. This seemed to occur concomitantly with the synthesis. alpha-Saturation of polyprenyl-P could not be achieved with the procedures employed. It is proposed that the synthesis of dolichol and dolichyl-P do not share the same terminal steps; saturation and terminal isoprene condensation occur in cooperation; and substrate concentration and pH influence the terminal enzyme(s) and the nature of the final product in the polyprenol biosynthesis.

Topics: Animals; Diterpenes; Dolichol Phosphates; Dolichols; Hydrogen-Ion Concentration; Liver; Male; Mevalonic Acid; Microsomes, Liver; NAD; Octoxynol; Ozone; Phosphoric Monoester Hydrolases; Polyethylene Glycols; Rats; Rats, Inbred Strains

The prenyltransferase involved in the biosynthesis of dolichyl phosphate has been characterized in Saccharomyces cerevisiae. Although the enzyme is predominantly membrane-bound, a significant percentage was found in the soluble fraction. The prenyltransferase preferentially utilizes farnesyl pyrophosphate as the allylic substrate and isopentenyl pyrophosphate as cosubstrate with half-maximal velocities obtained at 25 and 6.7 microM, respectively. The enzymatic activity is sensitive to sulfhydryl reagents and is inhibited by all detergents tested, except 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate at concentrations less than 5 mM. The product of the reaction has been characterized as an alpha-unsaturated polyprenyl pyrophosphate, containing 12-15 isoprene units, approximately two isoprene units shorter than the endogenous yeast dolichyl phosphate. The stereochemistry of addition of isoprene units by the prenyltransferase was shown to be cis by a comparison of the HPLC retention time for a pentadecaprenyl phosphate derived from the in vitro reaction product with that for an authentic mixture of alpha-cis- and alpha-trans-pentadecaprenyl phosphates.

Topics: Chromatography, High Pressure Liquid; Detergents; Dimethylallyltranstransferase; Dolichol Phosphates; Dolichols; Isomerism; Kinetics; Polyisoprenyl Phosphates; Saccharomyces cerevisiae; Substrate Specificity; Transferases

A study was conducted to determine whether repression of 3-hydroxy-3-methylglutaryl CoA reductase by a chronic high-cholesterol diet would deplete hepatic dolichol levels. Four-week-old male C57BL/6J mice were maintained on a control diet or a diet supplemented with 5% cholesterol. Animals from both groups were killed at various times and reductase activity and levels of free dolichol, dolichyl acyl ester, dolichyl phosphate, and ubiquinone were measured. The reductase activity was reduced by 90% within 1 week and remained depressed through 56 days. Initially, the levels of the free dolichol, acyl ester, phosphoryl ester, and ubiquinone were 7, 16, 5, and 80 micrograms/g liver, respectively. Early increases in the concentration of dolichyl phosphate and free dolichol were similar in both the cholesterol-fed and control groups. However, in the cholesterol-fed group the concentration of dolichyl acyl esters was only 50% of that in the control group by 7 days and it remained lower throughout the experiment. Total dolichol levels were lower by about 30%. Ubiquinone levels were transiently depressed at 7 days by 33% but returned to control levels by 4 weeks. After 56 days, the control values of dolichol and dolichyl phosphate remained constant whereas the dolichyl acyl ester levels continuously increased to a value of 133 micrograms/g of liver by 156 days. Subcellular fractionation of livers from 4-week-old mice indicated a lysosomal distribution of dolichol and dolichyl acyl ester and a lysosomal and microsomal distribution of dolichyl phosphate.

Topics: Animals; Cholesterol, Dietary; Diterpenes; Dolichol Phosphates; Dolichols; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Liver; Lysosomes; Male; Mice; Mice, Inbred C57BL; Microsomes, Liver

A procedure for the quantitative extraction of both dolichol and dolichyl phosphate (Dol-P) in plant tissue (soybean embryos) into diethyl ether from an alkaline saponification mixture is described. A complete and quantitative separation of total dolichol and total Dol-P is then obtained based on their respective solubilities in diethyl ether and water. After separation dolichol and Dol-P can both be analyzed and quantitated directly by reverse-phase HPLC on C18 columns without additional purification. The two major homologs of dolichol and Dol-P are those with 17 and 18 isoprene units. The total dolichol and total Dol-P contents of dry embryos were 96.3 +/- 0.8 and 5.3 +/- 0.1 micrograms/g, respectively. The post-HPLC recoveries for dolichol and Dol-P were 101 +/- 2 and 84 +/- 3% respectively, using [1-14C]dolichol and Dol-P containing 20 isoprene units as recovery standards. Dol-P estimations could be carried out on material equivalent to as little as 65 mg embryo tissue.

Topics: Chromatography, High Pressure Liquid; Diterpenes; Dolichol Phosphates; Dolichols; Ether; Glycine max; Plants; Polyisoprenyl Phosphates; Solubility; Water

Autopsy material from deceased individuals between ages 2 and 90 was used to prepare cerebellum, pons, and other selected regions of the brain, the spinal cord, and peripheral nerves. The concentration of dolichol in these different tissues varied greatly and the increase in concentration during the life span varied between 2.5- and 21-fold. In contrast, dolichyl-phosphate (dolichyl-P) was more evenly distributed in these tissues and its concentration increased to a moderate extent only during childhood. The level of cholesterol displayed smaller regional differences and decreased about 15% between ages 35 and 90. Differences in the total phospholipid content were limited. These results demonstrate enrichment and individual regulation of various lipids in specialized regions of the human brain. The independent regulation of dolichol and dolichyl-P levels in the brain and the possible role of dolichol in the function of the aging nerve cell are also emphasized.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aging; Brain Chemistry; Child; Child, Preschool; Cholesterol; Chromatography, High Pressure Liquid; Diterpenes; Dolichol Phosphates; Dolichols; Humans; Middle Aged; Phospholipids; Polyisoprenyl Phosphates; Tissue Distribution

Hyperplastic liver nodules were induced in rats by administration of an initiator (diethylnitrosamine or 3'-methyl-4-dimethylaminoazobenzene) and/or a promoter (phenobarbital) by the method reported by Tatematsu et al. (1983, Carcinogenesis 4, 381-386). The dolichol content in the liver and liver microsomes of the rats treated with the initiator were approx. 1.5-times higher than that of the control and rats treated with only the promoter. However, the composition of dolichols was not changed. The time course of the dolichyl phosphate concentration in the rat liver treated with both initiator and promoter showed a pattern different from that in the control liver, the initiator-treated liver or the promoter-treated liver. The main component of dolichyl phosphate in liver treated with both the initiator and promoter changed from that with 18 isoprene units to that with 19. It is suggested that the changes in liver dolichols and dolichyl phosphates may be related to the formation of hyperplastic liver nodules.

Topics: Acyl Coenzyme A; Animals; Diethylnitrosamine; Diterpenes; Dolichol Phosphates; Dolichols; Hepatectomy; Hyperplasia; Liver; Liver Neoplasms, Experimental; Liver Regeneration; Male; Mannosyltransferases; Methyldimethylaminoazobenzene; Microsomes, Liver; Phenobarbital; Polyisoprenyl Phosphates; Rats; Rats, Inbred F344

The content of dolichol and dolichyl phosphate in various human organs was analysed using autopsy samples. The reliability of these measurements was demonstrated by comparison with values for fresh biopsy material. Dolichol was present in all tissues investigated and the content was highest in the adrenal gland, pancreas, pituitary gland, testis and thyroid gland, ranging between 1.5 and 7.1 mg/g tissue. Dolichyl-P was detected in the various organs in highly variable amounts, ranging between 1 and 9% of the total dolichol content. While the main pattern of isoprene composition for dolichol and dolichyl-P was similar in individual organs, some variation was observed between tissues. Dolichol represents the largest lipid component in the pituitary gland, exceeding the total phospholipid content. The high concentrations of dolichol and dolichyl-P in human organs indicate that these lipids may play important roles in physiological and pathological cellular functions.

Topics: Adrenal Glands; Aged; Diterpenes; Dolichol Phosphates; Dolichols; Humans; Male; Pituitary Gland; Polyisoprenyl Phosphates; Testis; Thyroid Gland

Dolichols and glycosyl transferase activities were studied in rat liver fractions after treatment with the plasticizer di(2-ethylhexyl)phthalate, an inducer of peroxisomes and mitochondria. After a few weeks of treatment with 2% plasticizer in the diet, the amount of dolichol is more than doubled in the lysosomes but not in the microsomes while dolichyl-P decreased by 50% in the microsomes but not in the lysosomes. The isoprenoid pattern for dolichol and dolichyl-P, respectively, is modified to longer polyprenols in the two fractions as seen in the percent distribution of the individual isoprenes. Dolichyl-P and protein glycosylation by N-acetylglucosamine and mannose decreased considerably. Incubation with mixtures containing exogenous dolichyl-P did not increase protein glycosylation. Phthalate ester treatment for 2 years increased dolichol content above the control values even when the dose was decreased a hundred times, to 0.02%. The results demonstrate a compartmentalization of dolichol and dolichyl-P distribution, and the induction studies suggest that hepatocytes possess separate regulating mechanisms for these two compounds.

Topics: Animals; Diethylhexyl Phthalate; Diterpenes; Dolichol Phosphates; Dolichols; Hexosyltransferases; Liver; Lysosomes; Microsomes, Liver; Mitochondria, Liver; Phthalic Acids; Polyisoprenyl Phosphates; Rats; Rats, Inbred Strains; Time Factors

The regenerating liver presents a changed ability to use mevalonate 16 hr after partial hepatectomy. The dolichol content and its synthesis from mevalonate is increased, while no variation of dolichyl-P and ubiquinone parameters are detectable. The greater amount of mevalonate utilized to form dolichol, but not dolichyl-P, in this proliferating system, raises some questions about the physiological significance of these isoprenoid compounds and about their biosynthetic sequence.

Topics: Animals; Diterpenes; Dolichol Phosphates; Dolichols; Hepatectomy; Liver; Liver Regeneration; Male; Mevalonic Acid; Polyisoprenyl Phosphates; Rats; Rats, Inbred Strains; Time Factors

The effect of dolichol and dolichyl phosphate on fusion between large unilamellar vesicles comprised of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) was studied using a fluorescence resonance energy transfer assay. The influence of dolichyl phosphate on the transbilayer movement of DOPC in multilamellar vesicles (MLV) and large unilamellar vesicles (LUV) composed of DOPC and DOPE (1:2) was investigated by using the phosphatidylcholine-specific transfer protein. 31P-NMR and freeze-fracture electron microscopy were employed to study the macroscopic organization of DOPC and DOPE containing model membranes in the absence or presence of dolichyl phosphate. The results indicate that both dolichol and dolichyl phosphate enhance vesicle fusion in a comparable and concentration-dependent way; the amount of exchangeable PC from MLVs is increased by dolichyl phosphate, probably as a result of fusion processes; dolichyl phosphate destabilizes the bilayer organization in MLVs comprised of DOPE and DOPC, resulting in the formation of hexagonal (HII) phase and 'lipidic' particles.

Topics: Diterpenes; Dolichol Phosphates; Dolichols; Freeze Fracturing; Magnetic Resonance Spectroscopy; Membrane Fluidity; Membrane Fusion; Membrane Lipids; Membranes, Artificial; Phosphatidylcholines; Phosphatidylethanolamines; Polyisoprenyl Phosphates

Topics: Carcinoma, Hepatocellular; Diterpenes; Dolichol Phosphates; Dolichols; Humans; Liver; Liver Neoplasms; Phosphorylation

The effect of dolichols, polyprenols, dolichol esterified with fatty acids, and dolichyl phosphate on the structure and fluidity of model membranes was studied using 31P NMR, small-angle x-ray scattering, differential scanning calorimetry, and freeze-fracture electron microscopy. These studies suggest that dolichol and dolichol derivatives destabilize unsaturated phosphatidylethanolamine containing bilayer structures and promote hexagonal II phase formation; high concentrations of dolichol induce lipid structures characterized by "isotropic" 31P NMR and particulate fracture faces; dolichol, contrary to cholesterol, has no effect on the thermotropic behavior of membranes consisting of phosphatidylcholine, while dolichyl-P incorporation abolishes the transition from the gel to liquid crystalline phase in 1,2-dimyristoyl-sn-glycero-3-phosphocholine; both dolichol and dolichyl-P increase the fatty acid fluidity in phosphatidylethanolamine mixtures; the effect of dolichol on bilayer structure and fluidity is more pronounced with increasing number of isoprene residues; dolichol esters are only soluble to a limited extent in the bilayer and segregates into domains at low concentrations; the results are consistent with a localization of dolichyl-P in which the phosphate group is oriented to the water interphase. The induction of hexagonal II phase by dolichyl-P may elicit the transmembrane movement of glycosylated lipid intermediate.

Topics: Calorimetry, Differential Scanning; Diterpenes; Dolichol Phosphates; Dolichols; Esters; Fatty Acids; Freeze Fracturing; Humans; Magnetic Resonance Spectroscopy; Membrane Fluidity; Membrane Lipids; Membranes, Artificial; Microscopy, Electron; Models, Molecular; Phospholipids; Polyisoprenyl Phosphates; Scattering, Radiation; Terpenes

Topics: Aged; Chromatography, DEAE-Cellulose; Chromatography, High Pressure Liquid; Diterpenes; Dolichol Phosphates; Dolichols; Humans; Hydrolysis; Tissue Extracts

Topics: Animals; Diethylhexyl Phthalate; Diterpenes; Dolichol Phosphates; Dolichols; Liver; Phthalic Acids; Plasticizers; Rats

Hyperplastic nodules and hepatocarcinomas were produced in rat liver by 2-acetylaminofluorene-containing diet. The homogenates and isolated microsomes were analyzed for the content of lipid intermediates and glycosylation reactions. The dolichol content of hyperplastic nodules increases four times in the homogenate and six times in the microsomes. In developed hepatocarcinoma, the amount of dolichol was doubled. Concerning the distribution pattern of the polyprenols, there is a change in the relative amounts of dolichols with 18 and 19 residues. In contrast to the free alcohol, dolichyl phosphate was greatly decreased in nodules, a finding which might be explained by a decreased dolichol kinase and an increased dolichol monophosphatase activity. The percentage of total phosphorylated dolichol was related to the glycosylating capacity. In microsomes, mitochondria, and homogenate from normal liver and in homogenate from hyperplastic liver nodules, the percentages of dolichyl phosphate were 23, 2, 16, and 4, respectively. At maximal glycosylation in vitro, only part of the total dolichyl phosphate was glycosylated. Dolichol-mediated protein glycosylation exhibited a general decrease in the microsomes from nodules and cancer tissue; it is suggested that the main cause of the decrease is a shortage of the available dolichyl phosphate which is rate limiting and which also contributes to the synthesis of the modified oligosaccharide chain.

Topics: 2-Acetylaminofluorene; Animals; Carbohydrate Metabolism; Dolichol Phosphates; Dolichols; Liver Neoplasms; Male; Phosphoric Monoester Hydrolases; Phosphotransferases; Phosphotransferases (Alcohol Group Acceptor); Polyisoprenyl Phosphates; Proteins; Rats; Rats, Inbred Strains

Human ceroid lipofuscinosis (CL) is an inherited disease marked by cerebromacular degeneration and early death. We have utilized the canine model to investigate the possible role of dolichol and dolichyl phosphate in the developmental pathology of CL. We found that while brain levels of dolichol increase with age in both affected and unaffected dogs, the amount in the diseased animal was similar to that in controls. Brain levels of dolichyl phosphate ranged from 20 to 35 micrograms/g in control dogs at all ages examined, but increased substantially during development in the affected dogs, a value of 113 +/- 24 micrograms/g (mean +/- SD) being obtained in the end-stage animals. In addition to the results obtained in the canine model, dolichyl phosphate levels in human brain tissues from a 5-year-old with late infantile CL and from a 19-year-old with juvenile CL were found to be 153 and 382 micrograms/g, respectively, compared with a control that assayed 26 micrograms/g. The preliminary findings with human tissues provide further evidence for an association of elevated brain dolichyl phosphate levels with CL. Whether the increase is primary or secondary remains to be determined.

Topics: Adult; Animals; Brain Chemistry; Child, Preschool; Diterpenes; Dog Diseases; Dogs; Dolichol Phosphates; Dolichols; Heterozygote; Homozygote; Humans; Male; Microscopy, Fluorescence; Neuronal Ceroid-Lipofuscinoses; Phosphoric Monoester Hydrolases; Polyisoprenyl Phosphates

The thermotropic phase transition of dipalmitoylphosphatidylcholine vesicles reconstituted with dolichol or dolichyl phosphate was investigated as a function of the lipid-to-polyisoprenoid ratio by means of differential scanning calorimetry and fluorescence depolarization of the embedded probe 1,6-diphenyl-1,3,5-hexatriene. At the concentrations studied, dolichol and dolichyl phosphate lowered and broadened the transition temperature of dipalmitoylphosphatidylcholine bilayers. Dolichol was found to increase the motional freedom of the bilayer both below and above the transition temperature as determined by fluorescence depolarization. In contrast, low concentrations of dolichyl phosphate decreased the bilayer motional freedom below the transition temperature while high concentrations increased the motional freedom. Above the transition temperature, dolichyl phosphate decreased bilayer 'fluidity' at all concentrations. The data suggest that these polyisoprenoids perturb the bilayer lattice, with the neutral species dolichol increasing membrane 'fluidity', while dolichyl phosphate acts to 'stiffen' the membrane.

Topics: Calorimetry, Differential Scanning; Diphenylhexatriene; Diterpenes; Dolichol Phosphates; Dolichols; Fluorescence Polarization; Lipid Bilayers; Mathematics; Membrane Fluidity; Polyisoprenyl Phosphates; Pulmonary Surfactants; Temperature

The in vivo and in vitro synthesis and turnover of dolichol and dolichyl phosphate have been studied over the course of early development in sea urchin embryos. Synthesis of dolichol and dolichyl phosphate was studied in vivo and in vitro using [3H]acetate and [14C] isopentenylpyrophosphate, respectively, as precursors. Both the in vivo and in vitro results indicate that the principal labeled end product of de novo synthesis is the free alcohol, and that this alcohol is subsequently phosphorylated to produce dolichyl phosphate. The presence of 30 microM compactin inhibits the de novo synthesis of dolichol from [3H]acetate by greater than 90%, but has no effect on the incorporation of 32Pi into dolichyl phosphate for more than 6 h, thus suggesting that during this time interval the major source of dolichyl phosphate is preformed dolichol. The rate of turnover of the [3H]acetate-labeled polyisoprenoid backbone of dolichyl phosphate is very slow (t1/2 = 40-70 h). In contrast, the rate of loss of the [32P]phosphate headgroup is more rapid (t1/2 = 5.7-7.7 h) and increases over the course of development. Finally, dolichyl phosphate phosphatase activity has been measured in vitro. The activity of this enzyme, which can be distinguished from phosphatidic acid phosphatase, was found to increase as a function of development, in qualitative agreement with the increased turnover of 32P from dolichyl phosphate observed in vivo. These results suggest that the phosphate moiety of dolichyl phosphate is in a dynamic state, and that dolichol kinase and dolichyl phosphate phosphatase play key roles in regulating the cellular level of dolichyl phosphate.

Topics: Acetates; Animals; Diterpenes; Dolichol Phosphates; Dolichols; Fluorides; Phosphatidate Phosphatase; Phosphoric Monoester Hydrolases; Polyisoprenyl Phosphates; Sea Urchins

The dolichol and dolichyl phosphate (Dol-P) content of various tissues and liver subcellular fractions obtained from rats have been measured directly using high pressure liquid chromatographic methods developed in this laboratory. Spleen contained the highest concentration of dolichol, while other tissues including serum had smaller amounts. Although considerable differences in homologue distribution patterns were observed among the tissues examined, a number of purified subcellular fractions obtained from liver (nuclei, mitochondria, cytosol, and microsomes) exhibited a single common pattern. Only some 5% of liver dolichol appeared in the microsomal compartment of the cell where glycoprotein formation occurs, while 50% of the dolichol in this tissue was found in a lysosome-enriched fraction. The concentrations of dolichol present in liver nuclei, mitochondria, whole microsomes (also rough and smooth, endoplasmic recticulum (RER and SER, respectively), and cytosol were considerably lower (on a protein basis) than those present in whole liver. Besides the lysosome-enriched fraction, only plasma membranes and Golgi contained dolichol at concentrations equal to or greater than those present in liver homogenates. The low concentrations of dolichol found in microsomes suggest that the amounts of dolichol available for Dol-P formation via the CTP-dependent kinase reaction may be rate limiting. Most of the Dol-P in liver could be recovered in the microsomal fraction. Dol-P accounted for 4 and 40% of the sum of alcohol + dolichyl fatty acyl ester + Dol-P forms present in whole liver and in microsomes, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Diterpenes; Dolichol Phosphates; Dolichols; Glycoproteins; Liver; Microsomes, Liver; Phosphoric Monoester Hydrolases; Phosphotransferases; Phosphotransferases (Alcohol Group Acceptor); Polyisoprenyl Phosphates; Rats; Tissue Distribution

The rates of synthesis and tissue concentrations of dolichol derivatives differ markedly in testes and preputial glands from adult C57BL/6J mice. In testes, the rates of free dolichol, dolichyl acyl esters, and dolichyl phosphate synthesis were approximately 5,000, 4,000 and 2,000 dpm/3h/g, respectively. Comparable rates for preputial glands were 12,000, 60,000 and 0 dpm/3h/g. Thus in testes, dolichyl phosphate represented 15-20% of total dolichol synthesis, whereas no de novo dolichyl phosphate synthesis was detected in preputial glands. In testes, free dolichol was the predominant derivative synthesized; in preputial glands, 80% of dolichol synthesized was esterified to fatty acids. The concentration of total dolichol (free alcohol plus acyl esters) was 160 micrograms/g tissue in testes and 1270 micrograms/g tissue in preputial glands. In both tissues, 85-90% of dolichol was esterified to fatty acids, and no dolichyl phosphate was detected.

Topics: Animals; Diterpenes; Dolichol Phosphates; Dolichols; Exocrine Glands; Male; Mice; Mice, Inbred C57BL; Polyisoprenyl Phosphates; Testis

The biosynthesis of dolichol and dolichylmonophosphate in rat liver was studied using [3H]mevalonate as precursor. The radioactive precursor was either injected into the portal vein of the rat or added to the incubation medium containing isolated hepatocytes, followed by the isolation of microsomes and mitochondria from the liver or the hepatocytes. In both systems dolichol in microsomes was highly labeled after a short labeling period followed by a rapid decrease. During this period the labeling of mitochondrial dolichol was low. The specific radioactivity of dolichyl-P in microsomes of both systems was higher in the initial phase than in dolichol and increased further with time. The mitochondrial labeling was also increased but was at a much lower level.

Topics: Animals; Diterpenes; Dolichol Phosphates; Dolichols; Liver; Male; Mevalonic Acid; Microsomes, Liver; Mitochondria, Liver; Polyisoprenyl Phosphates; Rats; Rats, Inbred Strains