24-25-dihydroxyvitamin-d-3 and calcifediol-lactone

Topics: 24,25-Dihydroxyvitamin D 3; Animals; Bone and Bones; Calcifediol; Cartilage; Chick Embryo; Cholecalciferol; Dehydrocholesterols; Dihydroxycholecalciferols; Humans; Parathyroid Hormone; Vitamin D

The pathway from 25-hydroxyvitamin D3(25[OH]D3) to 25-hydroxyvitamin D3-26,23-lactone (25[OH]D3-26,23-lactone) is important in the renal degradation of vitamin D metabolites. Our objective was to investigate the regulation of 25(OH)D3 metabolism in the opossum kidney (OK) cell line which has been used for studying the actions of the calcium-regulating hormones. While the untreated OK cells did not produce 25(OH)D3 metabolites, the synthesis of the lactone was increased dose-dependently by 20h pretreatment with 1 alpha,25-dihydroxyvitamin D3 (1,25[OH]2D3), peaked at 10(-7) M 1,25(OH)2D3, and decreased with higher concentrations. Little production of 24,25-dihydroxyvitamin D3 (24,25[OH]2D3) was observed after any dose of 1,25(OH)2D3. The increase in the production of lactone induced by 10(-7) M 1,25(OH)2D3 was detectable at 2 h, peaked between 4 and 24 h, and decreased gradually until 48 h. Its induction was inhibited by actinomycin D and cycloheximide, suggesting that de novo protein synthesis is required for such induction. After treatment with 10(-7) M 1,25(OH)2D3 for 20 h, 24-hydroxylase (24-OHase) mRNA was not detected in OK cells, but was found evident in COS-7 cells (a renal cell line). Moreover, the COS-7 cells treated with 10(-7) M 1,25(OH)2D3 metabolized 25(OH)D3 to 24,25(OH)2D3. These results indicate that 1,25(OH)2D3 stimulates the synthesis of 25(OH)D3-26,23-lactone in a dose- and time-dependent manner, but does not induce the gene expression or activity of 24-OHase in OK cells.

Topics: 24,25-Dihydroxyvitamin D 3; Animals; Calcifediol; Calcitriol; Cell Line; Chlorocebus aethiops; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Female; Kidney; Opossums; Protein Synthesis Inhibitors; RNA, Messenger; Steroid Hydroxylases; Time Factors; Vitamin D3 24-Hydroxylase

A high-performance liquid chromatographic system is described for the baseline resolution of 25-hydroxyvitamin D3, 24(R),25-dihydroxyvitamin D3 and 25-hydroxyvitamin D3-26,23-lactone, the three principal circulating metabolites of vitamin D3 in the vitamin D-replete animal. The system is based upon a cyano-bonded phase packing and the solvent hexane--isopropanol--methanol (94:5:1). Of particular interest is the strong retention of carbonyl-containing vitamin D metabolites. The new system can be used for unequivocal analysis of vitamin D metabolites in plasma samples from clinical and animal studies and in the separation and identification of renal metabolites generated in vitro.

Topics: 24,25-Dihydroxyvitamin D 3; Animals; Binding, Competitive; Calcifediol; Chromatography, High Pressure Liquid; Diet; Dihydroxycholecalciferols; Kidney; Male; Protein Binding; Rats; Rats, Inbred Strains

Topics: 24,25-Dihydroxyvitamin D 3; Animals; Calcifediol; Calcitriol; Chickens; Chromatography, High Pressure Liquid; Dihydroxycholecalciferols; Hydroxycholecalciferols; Hydroxylation; Kidney; Tritium; Vitamin D Deficiency

1. Vitamin D and its metabolites were measured in the plasma of five species of rural domestic animals. 2. Concentration of 1,25-dihydroxyvitamin D was higher (P less than 0.01) in young animals (range 24-118 pg/ml, means +/- SD = 72.0 +/- 30.0) than in adult animals (range 14-67 pg/ml, means +/- SD = 40.2 +/- 22.6). 3. 25-Hydroxyvitamin D3-26,23 lactone was present only in the chick and the pig. 4. Unsheared sheep appeared to be inefficient utilizers of the photochemical conversion of 7-dehydrocholesterol to vitamin D3. 5. Conversion of 25-hydroxyvitamin D to 24,25-dihydroxyvitamin D was most efficient in species with high plasma phosphorus concentrations (pig, sheep).

Topics: 24,25-Dihydroxyvitamin D 3; Aging; Animals; Animals, Domestic; Calcifediol; Calcitriol; Cattle; Chickens; Dihydroxycholecalciferols; Female; Male; Sheep; Swine; Turkeys; Vitamin D

Here we report the use of newly developed and established techniques for the determination of plasma levels of a broad spectrum of vitamin D3 metabolites, including vitamin D3 and 25OHD3-lactone, in normal humans, chronic renal failure patients, and anephric subjects. The methodology described consisted of methanol-methylene chloride extraction, Lipidex-5000 chromatography with stepwise gradient elution, normal-phase HPLC with concave gradient elution, and sensitive ligand-binding assays. The results of the study strongly suggest an extrarenal source(s) for 24,25(OH)2D3 and 25,26(OH)2D3 and indicate that both 25OHD3-lactone and 1,25(OH)2D3 may be produced solely in the kidney of the human. Significant reductions or nondetectable plasma levels of vitamin D3 in the renal disease patients may reflect abnormalities in the hepatobiliary-intestinal and/or cutaneous metabolism of vitamin D.

Topics: 24,25-Dihydroxyvitamin D 3; Calcifediol; Calcitriol; Cholecalciferol; Dihydroxycholecalciferols; Humans; Hydroxycholecalciferols; Kidney Failure, Chronic; Methods; Nephrectomy

To elucidate the biosynthesis of 25-hydroxyvitamin D3-26,23-lactone, two known metabolites of 25-hydroxyvitamin D3--23,25-dihydroxyvitamin D3 and 25,26-dihydroxyvitamin D3--were incubated individually with kidney homogenate prepared from vitamin D-supplemented chickens, a preparation known to produce the lactone from 25-hydroxyvitamin D3. The 25-hydroxyvitamin D3-26,23-lactone produced in vitro was then separated, purified, identified, and quantitated by consecutive straight-phase and reverse-phase high-performance liquid chromatography. 23,25-Dihydroxyvitamin D3 is a far better substrate for production of 25-hydroxyvitamin D3-26,23-lactone than is 25,26-dihydroxyvitamin D3. Production of lactone is highly selective for the natural 23(S)-hydroxy-23,25-dihydroxyvitamin D3 while both epimers of 25,26-dihydroxyvitamin D3 resulted in small amounts of product comigrating with natural lactone. It appears that 23(S),25-dihydroxyvitamin D3, but not 25,26-dihydroxyvitamin D3, is a natural precursor in the synthesis of 25-hydroxyvitamin D3-26,23-lactone; this result also implies that the configuration of the lactone at C-23 is S.

Topics: 24,25-Dihydroxyvitamin D 3; Animals; Calcifediol; Chickens; Dihydroxycholecalciferols; Hydroxycholecalciferols; Kidney; Lactones

Topics: 24,25-Dihydroxyvitamin D 3; Animals; Calcifediol; Calcitriol; Cholecalciferol; Cytochrome P-450 Enzyme System; Dihydroxycholecalciferols; Humans; Hydroxycholecalciferols; Intestine, Small; Kidney; Mitochondria; Radioisotope Dilution Technique; Skin; Tritium; Vitamin D