calcimycin and lanthanum-chloride

Programmed cell death (PCD) is the destruction of unwanted cells through an intracellularly mediated process. Perforation formation in the lace plant (Aponogeton madagascariensis) provides an excellent model for studying developmentally regulated PCD. Ca

Topics: Alismatales; Apoptosis; Calcimycin; Calcium; Calcium Ionophores; Cell Death; Cell Tracking; Image Processing, Computer-Assisted; Lanthanum; Optical Imaging; Plant Leaves; Ruthenium Red

The unicellular cyanobacterium Synechocystis sp. PCC 6803 (Syn6803) exhibits photomovement through gliding motility. For a better understanding of photomovement in Syn6803, we examined the effects of Ca2+ on photoorientation and motility using a computer-assisted videomicroscope motion analysis system. When calcium ion was chelated from the basic motility medium by adding 0.5 mM ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), the photoorientation was completely inhibited, whereas the gliding motility remained approximately 70% of the control. Photoorientation impaired by EGTA was nearly recovered within 30 min upon addition of 1 mM Ca2+. The recovery of photoorientation by Ca2+ was mimicked by either Mn2+ or Mg2+ but not by Ba2+ or Sr2+. Lanthanum ion at 10 microM completely inhibited both phototactic orientation and gliding motility of Syn6803. Furthermore, pimozide (voltage-gated L-type calcium channel inhibitor), orthovanadate (calcium efflux blocker) and A23187 (calcium ionophore) partially inhibited phototactic orientation and gliding motility. Interestingly, photoorientation was prevented with increasing concentrations of calmodulin antagonist such as trifluoperazine (TFP) and chlorpromazine, but gliding motility was inhibited in proportion to the concentration of TFP. The results we present strongly indicate that Ca2+ plays a significant role in regulating the photomovement of Syn6803.

Topics: Calcimycin; Calcium; Calcium Channel Blockers; Calcium Channels, L-Type; Cations, Divalent; Chlorpromazine; Cyanobacteria; Lanthanum; Light; Movement; Trifluoperazine

Fructose-bisphosphate aldolase is a glycolytic enzyme whose activity increases in rice roots treated with gibberellin (GA). To investigate the relationship between aldolase and root growth, GA-induced root aldolase was characterized. GA3 promoted an increase in aldolase accumulation when 0.1 microM GA3 was added exogenously to rice roots. Aldolase accumulated abundantly in roots, especially in the apical region. To examine the effect of aldolase function on root growth, transgenic rice plants expressing antisense aldolase were constructed. Root growth of aldolase-antisense transgenic rice was repressed compared with that of the vector control transgenic rice. Although aldolase activity increased by 25% in vector control rice roots treated with 0.1 microM GA3, FBPA activity increased very little by 0.1 microM GA3 treatment in the root of aldolase-antisense transgenic rice. Furthermore, aldolase co-immunoprecipitated with antibodies against vacuolar H+ -ATPase in rice roots. In the root of OsCDPK13-antisense transgenic rice, aldolase did not accumulate even after treatment with GA3. These results suggest that the activation of glycolytic pathway function accelerates root growth and that GA3-induced root aldolase may be modulated through OsCDPK13. Aldolase physically associates with vacuolar H-ATPase in roots and may regulate the vacuolar H-ATPase mediated control of cell elongation that determines root length.

Topics: Blotting, Western; Calcimycin; Calcium; DNA, Antisense; Dose-Response Relationship, Drug; Fructose-Bisphosphate Aldolase; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Gibberellins; Immunoprecipitation; Ionophores; Lanthanum; Oryza; Plant Growth Regulators; Plant Proteins; Plant Roots; Plants, Genetically Modified; Protein Kinases; RNA, Messenger; Seedlings; Vacuolar Proton-Translocating ATPases

The biosynthesis of a phytoalexin, beta-thujaplicin, in Cupressus lusitanica cell cultures can be stimulated by a yeast elicitor, H(2)O(2), or methyl jasmonate. Lipoxygenase activity was also stimulated by these treatments, suggesting that the oxidative burst and jasmonate pathway may mediate the elicitor-induced accumulation of beta-thujaplicin. The elicitor signalling pathway involved in beta-thujaplicin induction was further investigated using pharmacological and biochemical approaches. Treatment of the cells with calcium ionophore A23187 alone stimulated the production of beta-thujaplicin. A23187 also enhanced the elicitor-induced production of beta-thujaplicin. EGTA, LaCl(3), and verapamil pretreatments partially blocked A23187- or yeast elicitor-induced accumulation of beta-thujaplicin. These results suggest that Ca(2+) influx is required for elicitor-induced production of beta-thujaplicin. Treatment of cell cultures with mastoparan, melittin or cholera toxin alone or in combination with the elicitor stimulated the production of beta-thujaplicin or enhanced the elicitor-induced production of beta-thujaplicin. The G-protein inhibitor suramin inhibited the elicitor-induced production of beta-thujaplicin, suggesting that receptor-coupled G-proteins are likely to be involved in the elicitor-induced biosynthesis of beta-thujaplicin. Indeed, both GTP-binding activity and GTPase activity of the plasma membrane were stimulated by elicitor, and suramin and cholera toxin affected G-protein activities. In addition, all inhibitors of G-proteins and Ca(2+) flux suppressed elicitor-induced increases in lipoxygenase activity whereas activators of G-proteins and the Ca(2+) signalling pathway increased lipoxygenase activity. These observations suggest that Ca(2+) and G-proteins may mediate elicitor signals to the jasmonate pathway, and the jasmonate signalling pathway may then lead to the production of beta-thujaplicin.

Topics: Acetates; Calcimycin; Calcium; Cells, Cultured; Cholera Toxin; Cupressus; Cyclopentanes; Egtazic Acid; Fungi; GTP Phosphohydrolases; GTP-Binding Proteins; Hydrogen Peroxide; Intercellular Signaling Peptides and Proteins; Lanthanum; Lipoxygenase; Monoterpenes; Oxylipins; Peptides; Plant Growth Regulators; Signal Transduction; Suramin; Tropolone; Verapamil; Wasp Venoms

The addition of Ca2+-antagonizers (La2+), Ca2+-ionophores (A23187) and Ca2+-complexing agents (EGTA) inhibited the formation of xylanase activity in resting mycelia of Trichoderma reesei. The inhibition by the ionophore was reversed by the addition of Ca2+ ions. A similar inhibitory effect was obtained by the addition of the calmodulin inhibitors, trifluoroperazine, chlorpromazine and quinacrine, hence suggesting that the observed effect of Ca2+ on xylanase formation occurred via calmodulin. The inhibition of xylanase formation by trifluoroperazine was accompanied by an inhibition of formation of the xyn2 transcript, and of the hph (hygromycin B-phosphotransferase-encoding) gene when fused downstream of the 5'-regulatory signals of the T. reesei xyn2 gene, indicating that calmodulin is required for xyn2 induction. At trifluoroperazine concentrations, which inhibited extracellular xylanase formation only slightly (about 30%), the cell-free extracts exhibited slightly increased xylanase activities. Subcellular fractionation showed that in these mycelia, the XYN II protein was distributed over a range of light vesicular fractions. This accumulated XYN II protein had the same Mr as the secreted, extracellular enzyme, indicating that it had already passed Golgi-located preprotein processing. Trifluoroperazine also specifically interfered with the endogenous, Ca2+-dependent phosphorylation of a 20-kDa protein, which was predominantly observed in cell-free extracts from mycelia growing on xylan. From these data, we conclude that calmodulin is required for xylanase II formation by T. reesei both at a transcriptional level as well as at a post-Golgi step of the secretory pathway. We also suggest that at least one of these two steps may be mediated via Ca2+-calmodulin-dependent phosphorylation.

Topics: Calcimycin; Calcium; Calmodulin; Chelating Agents; Chlorpromazine; Egtazic Acid; Ionophores; Lanthanum; Protein Kinases; Quinacrine; Subcellular Fractions; Transcription, Genetic; Trichoderma; Trifluoperazine; Xylan Endo-1,3-beta-Xylosidase; Xylosidases

An in vitro technique for the measurement of calcium uptake into the maternal-facing fetal chorionic membrane (apical trophoblast) was used to study the relationship between calcium uptake and stage of pregnancy in the sheep. The effects on calcium uptake of varying calcium concentration and temperature of the incubation medium, of adding calcium channel blockers or heavy metals (lanthanum and nickel) or calcium ionophore/agonist were also studied. The data indicate a saturable calcium uptake process, plateauing after 15 min incubation. This uptake remained constant throughout the last third of gestation until a significant fall in uptake was noted during the final week prior to parturition. This uptake was not due to extracellular cellular diffusion since there was no significant uptake of tritiated inulin over the same period in each case. Calcium uptake in this system was also shown to be a temperature dependent process which was abolished at temperatures of 0-4 degrees C. A decrease in calcium concentration to 0.12 mM in the incubation medium also caused a corresponding decrease in calcium uptake to 21 per cent of control (1.2 mM). The addition of the heavy metals lanthanum and nickel also significantly reduced calcium uptake as did the calcium channel blockers verapamil, metoprolol and diltiazem. The calcium channel ionophore A23187 increased calcium uptake into the material facing chorion. Although the interplacentomal chorion may not be representative of the whole of the placental unit, it clearly contains a specific calcium uptake process under local physiological control. The blocking of calcium uptake by the specific I-type calcium channel blocker verapamil may indicate the presence of I-type channels of unusually low sensitivity since the concentration needed to block them was much higher than would be required for excitable I-type channels in isolated cells.

Topics: 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; Animals; Biological Transport; Calcimycin; Calcium; Calcium Channel Agonists; Calcium Channel Blockers; Chorion; Female; Gestational Age; Ionophores; Kinetics; Lanthanum; Nickel; Placenta; Pregnancy; Sheep; Temperature; Thapsigargin

Increasing clinical and experimental evidence suggests a multifunctional role of calcium in determining the response of the arterial intima to atherogenic stimuli. In this study, an endothelial cell (EC)-smooth muscle cell (SMC) bilayer model of the arterial wall was used to investigate the effect of calcium manipulation on the sequestration of 125I-labeled LDL within the subendothelial space. Bilayer cell cultures were exposed to EGTA (0.25-2.0 mM), ionophore A23187 (5 x 10(-6) M), lanthanum chloride (0.1 mM), and trifluoperazine (TFP; 0.25 microM). The movement of 125I-labeled LDL (10 micrograms/ml) through the endothelial barrier was measured, as was the binding and cellular uptake of 125I-labeled LDL by each cell type. Extracellular Ca2+ chelation with EGTA and intracellular Ca2+ mobilization with A23187 both increased EC permeability to LDL (P < 0.05; P = 0.0001, respectively), while not significantly affecting EC binding or uptake of lipoprotein. Conversely, these agents increased SMC uptake of LDL (P < 10(-7); P < 10(-8), respectively). Calcium blockade with lanthanum chloride had the opposite effect, reducing EC permeability (P = 0.011) and SMC uptake (P < 10(-5)), while increasing EC uptake (P = 0.016). TFP, a calmodulin inhibitor, had an effect similar to A23187, although reducing SMC uptake of LDL (P = 0.015). Alteration of the calcium gradient across the plasma membrane appears to influence EC permeability. This effect may be stabilized by Ca2+ blockade or calmodulin regulation of cytoplasmic Ca2+. Additional anti-atherogenic effects of calcium blockade may include a reduction in SMC uptake by the SMC.

Topics: Animals; Aorta; Calcimycin; Calcium; Calmodulin; Cattle; Cell Count; Cell Membrane Permeability; Egtazic Acid; Endothelium, Vascular; Lanthanum; Lipoproteins, LDL; Monocytes; Muscle, Smooth; Trifluoperazine

The fundamental question of gravitational biology is how do plants perceive a gravity. Recent experimental results have demonstrated that Ca second-messenger system has an essential role in induction of graviresponsiveness. Our data, that stimuli of various nature cause a rise of hyaloplasm Ca level revealed by means of pyroantimonate method, as well as complete inhibition of the gravitropism in roots of pea seedlings, provide indirect but consistent evidence of this role of Ca ions. A possible explanation for these results is that they may be due to an unbalanced and undirectional influx of Ca ions in statocytes from cell walls or from intracellular Ca stores, while in the presence of the Earths 1 g vector, this process occurs directionally, along this vector. It is possible that a target for the gravity stimulus is the flux mechanism of Ca to statocytes, including participation of the phosphatidylinositol system and calmodulin. The data that have become available from space flight experiments will be reviewed and an attempt will be made to compare these results with ground-based observations.

Topics: Calcimycin; Calcium; Chelating Agents; Coloring Agents; Egtazic Acid; Gravitation; Gravitropism; Gravity Sensing; Ionophores; Lanthanum; Pisum sativum; Plant Roots; Rotation; Ruthenium Red; Second Messenger Systems

Cultures of mouse Neuro-2a neuroblastoma cells treated with 3-6 mM extracellular Ca2+ exhibited enhanced neurite extension characterized by increased neurite numbers and lengths. The ganglioside GM1 potentiated the effect of extracellular Ca2+ by increasing further the number and length of the neurites formed in response to exogenous Ca2+. Maximal neuritic numbers were achieved with 4 mM Ca2+ while the longest neurites were observed in medium containing 4-6 mM Ca2+. Stimulation of the Ca2+ influx with the ionophore A23187 or the amino acid taurine also enhanced neurite formation and GM1 potentiated these actions. Transmission electron microscopy revealed numerous microtubules and neurofilaments in neurites and microfilaments with the spine-like processes along fine neuritic branches and in the filopodia of growth cones. Neuritic varicosities and growth cones contained a variety of vesicles. All of these structures were increased in the presence of GM1 and were increased further by extracellular Ca2+ or A23187. The ability of GM1 to enhance neuritogenesis was diminished by EGTA or Ruthenium red. Similarly, the effect of GM1 was diminished or abolished by Ca2+ channel blockers such as CdCl2 or LaCl3. X-ray microprobe analysis revealed that GM1 alone enhanced intracellular levels of total ionic and membrane bound Ca2+, perhaps accounting for the increased neuritogenesis observed under conditions in which Ca2+ was manipulated. The present study suggest that the neuritogenic action of GM1 is Ca2+ dependent.

Topics: Animals; Axons; Cadmium; Cadmium Chloride; Calcimycin; Calcium; Cell Differentiation; Cell Line; Egtazic Acid; G(M1) Ganglioside; Intermediate Filaments; Lanthanum; Mice; Microtubules; Neuroblastoma; Neurons; Ruthenium Red; Taurine

LaATP is shown to be an effective inhibitor of the calcium ATPase of sarcoplasmic reticulum because the binding of LaATP to cE.Ca2 results in the formation of lanthanum phosphoenzyme, which decays slowly. Steady-state activity of the calcium ATPase in leaky sarcoplasmic reticulum vesicles is inhibited 50% by 0.16 microM LaCl3 (15 nM free La3+, 21 nM LaATP) in the presence of 25 microM Ca2+ and 49 microM MgATP (5 mM MgSO4, 100 mM KCl, 40 mM 4-morpholinepropanesulfonic acid, pH 7.0, 25 degrees C). However, 50% inhibition of the uptake of 45Ca and phosphorylation by [gamma-32P]ATP in a single turnover experiment requires 100 microM LaCl3 (28 microM free La3+) in the presence of 25 microM Ca2+; this inhibition is reversed by calcium but inhibition of steady-state turnover is not. Therefore, binding of La3+ to the cytoplasmic calcium transport site is not responsible for the inhibition of steady-state ATPase activity. The addition of 6.7 microM LaCl3 (1.1 microM free La3+) has no effect on the rate of dephosphorylation of phosphoenzyme formed from MgATP and enzyme in leaky vesicles, while 6.7 mM CaCl2 slows the rate of phosphoenzyme hydrolysis as expected; 6.7 microM LaCl3 and 6.7 mM CaCl2 cause 95 and 98% inhibition of steady-state ATPase activity, respectively. This shows that inhibition of ATPase activity in the steady state is not caused by binding of La3+ to the intravesicular calcium transport site of the phosphoenzyme. Inhibition of ATPase activity by 2 microM LaCl3 (0.16 microM free La3+, 0.31 microM LaATP) requires greater than 5 s, which corresponds to approximately 50 turnovers, to reach a steady-state level of greater than or equal to 80% inhibition. Inhibition by La3+ is fully reversed by the addition of 0.55 mM CaCl2 and 0.50 mM EGTA; this reactivation is slow with t1/2 approximately 9 s. Two forms of phosphoenzyme are present in reactions that are partially inhibited by La3+: phosphoenzyme with Mg2+ at the catalytic site and phosphoenzyme with La3+ at the catalytic site, which undergo hydrolysis with observed rate constants of greater than 4 and 0.05 s-1, respectively. We conclude, therefore, that La3+ inhibits steady-state ATPase activity under these conditions by replacing Mg2+ as the catalytic ion for phosphoryl transfer. The slow development of inhibition corresponds to the accumulation of lanthanum phosphoenzyme. Initially, most of the enzyme catalyzes MgATP hydrolysis, but the fraction of enzyme with La3+ bound to the catalytic site gradua

Topics: Adenosine Triphosphate; Animals; Calcimycin; Calcium Chloride; Calcium-Transporting ATPases; Cobalt; Egtazic Acid; Kinetics; Lanthanum; Magnesium; Muscles; Phosphorylation; Protein Binding; Rabbits; Sarcoplasmic Reticulum

A factor(s) extracted from the third instar larval brains of the dipteran species Sarcophaga bullata and Drosophila melanogaster causes a dose-dependent reduction of juvenile hormone (JHB3) biosynthesis by isolated ring glands in vitro. In situ, this factor is presumably neuronally transmitted from the brain to ring gland. The allatostatic effect of the brain factor is reversible in vitro and may be overcome partially by the JHB3 precursor farnesoic acid. Agents which act to increase the intracellular levels of cAMP (3-isobutyl-1-methylxanthine (MIX), forskolin, 8-benzoyl cAMP) all caused the reduction of JHB3 synthesis in vitro in a reversible manner. The inhibitory effect of increased levels of cAMP was overcome by the addition of farnesoic acid to the culture medium. The dependence of JHB3 synthesis on extracellular calcium was demonstrated by incubation of ring glands in the presence of the Ca2+ channel blocker lanthanum chloride, and in Ca2(+)-free medium containing EGTA. The inclusion of farnesoic acid abolished the zero Ca2+ effect completely. However, the Ca2+ ionophore A23187 inhibited JHB3 production in medium containing Ca2+, suggesting that elevated intracellular levels of Ca2+ also suppress JHB3 production. This latter inhibition could not be reversed completely by farnesoic acid.

Topics: Animals; Brain; Calcimycin; Calcium; Calcium Channel Blockers; Cyclic AMP; Drosophila melanogaster; Endocrine Glands; Fatty Acids, Unsaturated; Juvenile Hormones; Lanthanum

Arresting P815 mastocytoma cell growth with N6, O2'-dibutyryladenosine 3':5' cyclic monophosphate (db cAMP) and theophylline increased 45Ca2+ uptake and efflux by the cells (i.e, Ca2+ cycling) without altering cytoplasmic free Ca2+ concentrations or the amount or distribution of protein kinase C in the cells. Attempts to identify the Ca2+ channels involved using a wide variety of drugs were unsuccessful. However, the inhibitory effect of db cAMP on growth was greatly increase in medium containing low Ca2+ concentrations, confirming that interactions between Ca2+ and cyclic AMP can affect mastocytoma cell growth.

Topics: Animals; Bucladesine; Calcimycin; Calcium; Calcium Channels; Calcium Radioisotopes; Calcium-Transporting ATPases; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Cell Division; Cytoplasm; Egtazic Acid; Lanthanum; Mast-Cell Sarcoma; Mice; Protein Kinase C; Ruthenium Red; Theophylline; Tumor Cells, Cultured; Vanadates

The red light requirement for positive gravitropism in roots of corn (Zea mays cv "Merit") provides an entry for examining the participation of calcium in gravitropism. Applications of calcium chelators inhibit the light response. Calcium channel blockers (verapamil, lanthanum) can also inhibit the light response, and a calcium ionophore, A23187, can substitute for light. One can substitute for red light by treatments which have elsewhere been shown to trigger Ca2+ influx into the cytosol, e.g. heat or cold shock. Agents which are known to be agonists of the phosphatidylinositol second messenger system (serotonin, 2,4-dichlorophenoxyacetic acid, deoxycholate) can each partially substitute for the red light, and Li+ can inhibit the light effect. These experiments suggest that the induction of positive gravitropism by red light involves a rise in cytoplasmic Ca2+ concentration, and that a contribution to this end may be made by the phosphatidylinositol second messenger system.

Topics: Calcimycin; Calcium; Calcium Channel Blockers; Calcium Chloride; Chelating Agents; Darkness; Edetic Acid; Egtazic Acid; Gravitropism; Ionophores; Lanthanum; Light; Phosphatidylinositols; Plant Roots; Second Messenger Systems; Verapamil; Zea mays

In intact human lymphocytes, cyclic AMP accumulation in response to isoproterenol was inhibited by 5 mM EDTA, by deletion of calcium ions from the medium and by 1 mM lanthanum chloride, but not by 1 microM verapamil or by 10 microM nifedipine. A23187 caused a modest increase in cyclic AMP content. Exposure of lymphocytes to 5 microM 1-isoproterenol desensitized the cells to subsequent beta-adrenergic stimulation, reducing cyclic AMP accumulation. With higher concentrations of 1-isoproterenol (50 microM), receptor density was reduced as well. None of the above agents attenuated losses in agonist-stimulated cyclic AMP accumulation induced by treatment with 5 microM isoproterenol for 90 min. These data suggest that calcium ions, both those present in the extracellular medium and those bound to the plasma membrane, are required for isoproterenol-stimulation of adenylate cyclase. In addition, it appears that neither the presence of extracellular calcium ions nor full activation of adenylate cyclase are required for desensitization.

Topics: 1-Methyl-3-isobutylxanthine; Calcimycin; Calcium; Cells, Cultured; Cyclic AMP; Edetic Acid; Humans; Isoproterenol; Kinetics; Lanthanum; Lymphocytes; Nifedipine; Receptors, Adrenergic, beta; Verapamil

The role of cAMP and calcium in the induction of ornithine decarboxylase (ODC, E.C.4.1.1.17) activity in the osteogenic sarcoma cell line, UMR 106-01, was studied, with particular interest for parathyroid hormone (PTH). PTH and forskolin dose-dependently induced the ODC activity and the cAMP production. Protein synthesis is involved in the effect of PTH and forskolin on ODC activity but not on cAMP production. Using quin2 we showed that 20 nM PTH and 10 microM forskolin increased the intracellular ionized calcium concentration ([Ca2+]i), thereby offering the possibility for calcium to play a role as cellular mediator in the action of PTH and forskolin in bone. Data obtained with A23187 showed that solely an increase of the [Ca2+]i is not sufficient to stimulate basal or potentiate PTH- and forskolin-induced ODC activity. However, the effects of calcium channel blockers and EGTA on basal and PTH- and forskolin-induced ODC activity point to a specific role for calcium. Moreover, the effects of calcium channel blockers and EGTA on basal and PTH- and forskolin-induced cAMP production indicate that the involvement of calcium in the induction of ODC activity is primarily located at another site than the adenylate cyclase. These data indicate that calcium is involved in the control of basal ODC activity. Furthermore, these data suggest that both cAMP and calcium are involved in the induction of ODC activity by PTH and forskolin. More precisely, ODC activity in UMR 106-01 cells can be induced by PTH and forskolin via a calcium-dependent cAMP messenger system.

Topics: Adenylyl Cyclases; Animals; Calcimycin; Calcium; Cell Line; Colforsin; Cyclic AMP; Dose-Response Relationship, Drug; Lanthanum; Ornithine Decarboxylase; Osteoblasts; Parathyroid Hormone; Rats; Verapamil

The role of calcium in the regulation of sodium-dependent high-affinity uptake of choline was assessed in vitro in slices of the rat brain, by measuring the specific binding of [3H]hemicholinium-3 ([3H]HCh-3) and the uptake of [3H]choline. Depolarization with potassium of slices of hippocampus, cortex, or striatum significantly increased the specific binding of [3H]HCh-3 when compared to control slices. However, the observed potentiation of specific binding of [3H]HCh-3 was markedly inhibited by the removal of calcium from the incubation medium in cortex or hippocampus, but not in slices of striatum. Alterations in the uptake of [3H]choline directly paralleled the observed changes in the specific binding of [3H]HCh-3 in striatum of the rat and were unaffected by the reduction of calcium in the incubation medium. The inorganic calcium channel antagonists, cadmium and cobalt, but not magnesium, zinc, manganese or lanthanum, significantly inhibited the 40 mM potassium chloride-induced stimulation of the binding of [3H]HCh-3 in the striatum. Finally, the calcium ionophore A23187 significantly increased the binding of [3H]HCh-3 in slices of striatum, either in the presence or absence of calcium in the bathing medium. This study demonstrates regional differences in the role of extracellular calcium in the regulation of the uptake of choline and suggests the involvement of intracellular release of calcium in the in vitro regulation of the sodium-dependent high-affinity uptake of choline in the striatum.

Topics: Animals; Brain; Calcimycin; Calcium; Calcium Channel Blockers; Cations, Divalent; Choline; Hemicholinium 3; Lanthanum; Male; Metals; Potassium Chloride; Rats; Rats, Inbred Strains

The metabolism of calcium has been investigated in the Ehrlich Ascites Tumour Cells (ATC). ATC extrude Ca2+ actively by an energy-dependent mechanism, supported by both respiration and glycolysis. Extrusion takes place even against a very steep concentration gradient (10 mM Ca2+). Cell calcium content is decreased by monovalent cations (Na+,K+ and Li+), which act independently from their metabolic effects. La3+ inhibits ATC Ca2+ extrusion whereas Ruthenium Red slightly decreases cell calcium content. The antibiotic ionophore A 23187 strongly increases ATC Ca2+ level. the metabolism of other divalent cations (Mg2+, Sr2+ and Mn2+) has been studied. Mg2+ does not show appreciable changes in the various metabolic conditions tested, while Mn2+ and Sr2+ behave quite differently from Ca2+, suggesting a different distribution of these cations in ATC. The experimental findings indicate that Ehrlich Ascites Tumour Cells regulate their calcium content by mechanisms related to plasma membranes while the size and activity of mitochondrial compartment is of minor importance.

Topics: Animals; Calcimycin; Calcium; Carcinoma, Ehrlich Tumor; Cations, Divalent; Cell Membrane; Lanthanum; Magnesium; Manganese; Mice; Potassium; Sodium; Strontium