Showing papers on "Vanadate published in 1985"
TL;DR: Cardiac performance was depressed in the untreated diabetic animals, but the cardiac performance of the vanadate-treated diabetic animals was not significantly different from that of nondiabetic controls, so vanadates controlled the high blood glucose and prevented the decline in cardiac performance due to diabetes.
Abstract: The trace element vanadium has an unclear biological function. Vanadate, an oxidized form of vanadium, appears to have an insulin-like action. The effect of vanadate on blood glucose and cardiac performance was assessed in female Wistar rats 6 weeks after they were made diabetic with streptozotocin. When vanadate was administered for a 4-week period to the diabetic rats, their blood glucose was not significantly different from that of nondiabetic controls despite a low serum insulin. In contrast, blood glucose was increased about threefold in the diabetic rats that were not treated with vanadate; these rats also had low insulin levels. Cardiac performance was depressed in the untreated diabetic animals, but the cardiac performance of the vanadate-treated diabetic animals was not significantly different from that of nondiabetic controls. Thus vanadate controlled the high blood glucose and prevented the decline in cardiac performance due to diabetes.
699 citations
TL;DR: Addition of vanadate to the culture medium of NRK-1 cells resulted in a maximal 40-fold increase in the level of phosphotyrosine in cell protein and induced transformation as evidenced by four criteria: generation of a highly refractile morphology, decreased density-dependent growth inhibition, increased rates of uptake of 2-deoxyglucose, and growth in the absence of a solid support.
317 citations
TL;DR: Results provide compelling evidence that a pH gradient generated by the H(+)-ATPase drives Ca(2+) accumulation into right-side-out tonoplast vesicles via a Ca( 2+)/H(+) antiport.
Abstract: Two types of ATP-dependent calcium (Ca 2+ ) transport systems were detected in sealed microsomal vesicles from oat roots. Approximately 80% of the total Ca 2+ uptake was associated with vesicles of 1.11 grams per cubic centimeter and was insensitive to vanadate or azide, but inhibited by NO 3 − . The remaining 20% was vanadate-sensitive and mostly associated with the endoplasmic reticulum, as the transport activity comigrated with an endoplasmic reticulum marker (antimycin A-insensitive NADH cytochrome c reductase), which was shifted from 1.11 to 1.20 grams per cubic centimeter by Mg 2+ . Like the tonoplast H + -ATPase activity, vanadate-insensitive Ca 2+ accumulation was stimulated by 20 millimolar Cl − and inhibited by 10 micromolar 4,4′-diisothiocyano-2,2′-stilbene disulfonic acid or 50 micromolar N,N′ -dicyclohexylcarbodiimide. This Ca 2+ transport system had an apparent K m for Mg-ATP of 0.24 millimolar similar to the tonoplast ATPase. The vanadate-insensitive Ca 2+ transport was abolished by compounds that eliminated a pH gradient and Ca 2+ dissipated a pH gradient (acid inside) generated by the tonoplast-type H + -ATPase. These results provide compelling evidence that a pH gradient generated by the H + -ATPase drives Ca 2+ accumulation into right-side-out tonoplast vesicles via a Ca 2+ /H + antiport. This transport system was saturable with respect to Ca 2+ ( K m apparent = 14 micromolar). The Ca 2+ /H + antiport operated independently of the H + -ATPase since an artifically imposed pH gradient (acid inside) could also drive Ca 2+ accumulation. Ca 2+ transport by this system may be one major way in which vacuoles function in Ca 2+ homeostasis in the cytoplasm of plant cells.
153 citations
TL;DR: Compared with insulin, vanadate increased glucose uptake, glycogen synthesis and glycolysis to a lesser degree, but caused a greater stimulation of lactate and glucose oxidation, and unlike insulin,Vanadate did not change either protein synthesis or degradation.
Abstract: To determine if vanadate has insulin-like actions in skeletal muscle, we measured its effects on glucose and protein metabolism in epitrochlearis muscles of rats. Compared with insulin, vanadate increased glucose uptake, glycogen synthesis and glycolysis to a lesser degree, but caused a greater stimulation of lactate and glucose oxidation. Unlike insulin, vanadate did not change either protein synthesis or degradation. These different metabolic responses could be related to the different pattern of insulin-receptor phosphorylation caused by insulin and vanadate.
148 citations
TL;DR: The transport activity of purified Na+K+‐ATPase was investigated by measuring the electrical pump current induced on black lipid membranes and the transient photoresponse indicates that the discs and the underlying membrane are capacitatively coupled.
Abstract: The transport activity of purified Na+K+-ATPase was investigated by measuring the electrical pump current induced on black lipid membranes. Discs containing purified Na+K+-ATPase from pig kidney were attached to planar lipid bilayers in a sandwich-like structure. After the addition of only microM concentrations of an inactive photolabile ATP derivative [P3-1-(2-nitro)phenylethyladenosine 5'-triphosphate, caged ATP] ATP was released after illumination with u.v.-light, which led to a transient current in the system. The transient photoresponse indicates that the discs and the underlying membrane are capacitatively coupled. Stationary pump currents were obtained after the addition of the H+, Na+ exchanging agent monensin together with valinomycin to the membrane system, which increased the permeability of the black lipid membrane for the pumped ions. In the absence of ADP and Pi the half saturation for the maximal photoeffect was obtained at 6.5 microM released ATP. The addition of ADP decreased the pump activity. Pump activity was obtained only in the presence of Mg2+ together with Na+ and Na+ and K+. No pump current was obtained in the presence of Mg2+ together with K+. The electrical response was blocked completely by the Na+K+-ATPase-specific inhibitors vanadate and ouabain. No pump currents were observed with a chemically modified protein, which was labelled on the ATP binding site with fluoresceine isothiocyanate. The method described offers the possibility of investigating by direct electrical measurements ion transport of Na+K+-ATPase with a large variety of different parameters.
131 citations
TL;DR: The sensitivity of both ATPases to ADP suggests that under conditions of restricted energy supply H(+)-ATPase activity may be reduced by increases in ADP levels rather than by decreases in ATP levels per se.
Abstract: Two distinct membrane fractions containing H + -ATPase activity were prepared from red beet. One fraction contained a H + -ATPase activity that was inhibited by NO 3 − while the other contained a H + -ATPase inhibited by vanadate. We have previously proposed that these H + -ATPases are associated with tonoplast (NO 3 − -sensitive) and plasma membrane (vanadate-sensitive), respectively. Both ATPase were examined to determine to what extent their activity was influenced by variations in the concentration of ATPase substrates and products. The substrate for both ATPase was MgATP 2− , and Mg 2+ concentrations in excess of ATP had only a slight inhibitory effect on either ATPase. Both ATPases were inhibited by free ATP ( i.e. ATP concentrations in excess of Mg 2+ ) and ADP but not by AMP. The plasma membrane ATPase was more sensitive than the tonoplast ATPase to free ATP and the tonoplast ATPase was more sensitive than the plasma membrane ATPase to ADP. Inhibition of both ATPases by free ATP was complex. Inhibition of the plasma membrane ATPase by ADP was competitive whereas the tonoplast ATPase demonstrated a sigmoidal dependence on MgATP 2− in the presence of ADP. Inorganic phosphate moderately inhibited both ATPases in a noncompetitive manner. Calcium inhibited the plasma membrane but not the tonoplast ATPase, apparently by a direct interaction with the ATPase rather than by disrupting the MgATP 2− complex. The sensitivity of both ATPases to ADP suggests that under conditions of restricted energy supply H + -ATPase activity may be reduced by increases in ADP levels rather than by decreases in ATP levels per se. The sensitivity of both ATPases to ADP and free ATP suggests that modulation of cytoplasmic Mg 2+ could modulate ATPase activity at both the tonoplast and plasma membrane.
98 citations
TL;DR: Proton translocation by resealed chromaffin-granule 'ghosts', measured by uptake of methylamine or by quenching of the fluorescence of 9-amino-6-chloro-2-methoxyacridine, is supported by the hydrolysis of ATP or ITP, and inhibited by quercetin or alkylating agents, but not by vanadate.
Abstract: Chromaffin-granule membranes contain two ATPases, which can be separated by (NH4)2SO4 fractionation after solubilization with detergents, or by phase segregation in Triton X-114. ATPase I (Mr 400000) is inhibited by trialkyltin, quercetin and alkylating agents, and hydrolyses both ATP and ITP. It contains up to five types of subunit, including a low-Mr hydrophobic polypeptide that reacts with dicyclohexylcarbodi-imide; these subunits are unrelated to those of mitochondrial F1F0-ATPase, as judged by size and reaction with antibodies. ATPase II (Mr 140000) is inhibited by vanadate, and is specific for ATP; it has not been extensively purified. Proton translocation by resealed chromaffin-granule 'ghosts', measured by uptake of methylamine or by quenching of the fluorescence of 9-amino-6-chloro-2-methoxyacridine, is supported by the hydrolysis of ATP or ITP, and inhibited by quercetin or alkylating agents, but not by vanadate. ATPase I must therefore be the proton translocator involved in the uptake of catecholamines and possibly of other components of the chromaffin-granule matrix, whereas ATPase II does not translocate protons.
87 citations
TL;DR: A comparison of the properties of the high affinity (Ca2+-Mg2+)-ATPase with those of the liver plasma membrane ATP-dependent Ca2+ transport activity reconstituted into artificial liposomes suggests that this high affinity
86 citations
TL;DR: It is concluded that the Golgi of corn coleoptiles contains a KCl-stimulated H(+)-ATPase which can acidify the interior of Golgi cisternae and associated vesicles.
Abstract: Corn (Zea mays L. cv Trojan T929) coleoptile membranes were fractionated on sucrose density gradients, and ATP-dependent proton pumping activity was localized by the techniques of [(14)C]methylamine uptake and quinacrine fluorescence quenching. Two peaks of proton pumping activity were detected: a light peak (1.07 grams/cubic centimeter) corresponding to the previously characterized tonoplast-type H(+)-ATPase, and a second peak (1.13 grams/cubic centimeter) which coincided with the Golgi markers, latent UDPase, and glucan synthase I. The second peak was lighter than that of the plasma membrane marker, uridine diphosphoglucose-sterol glucosyltransferase (1.16 grams/cubic centimeter) and was not inhibited by vanadate, an inhibitor of the plasma membrane ATPase. The activity was also better correlated with the Golgi cisternae marker, glucan synthase I, than with latent UDPase, a secretory vesicle marker, but a secretory vesicle location cannot be ruled out. The tonoplast-type and Golgi proton pumps were similar in several respects, including a pH optimum at 7.2, stimulation by chloride, inhibition by diethylstilbestrol and N,N'-dicyclohexylcarbodiimide (DCCD), insensitivity to oligomycin and azide, and nucleotide specificity for Mg(2+)-ATP. However, the Golgi H(+) pump was much less sensitive to nitrate and iodide, and more sensitive to the anion channel blockers, 4-acetamido-4'-isothiocyano-2,2'-stilbene sulfonic acid (SITS) and 4,4'-diisothiocyano-2,2'-stilbene disulfonic acid (DIDS) than the tonoplast-type H(+)-pump. The Golgi pump, but not the tonoplast-type pump, was stimulated by valinomycin in the presence of KCl. It is concluded that the Golgi of corn coleoptiles contains a KCl-stimulated H(+)-ATPase which can acidify the interior of Golgi cisternae and associated vesicles.
84 citations
TL;DR: The observations indicate that, in addition to monovanadate, the di-, tetra- and deca-vanadates are also bound to sarcoplasmic-reticulum membranes with high affinity.
Abstract: The binding of mono- and oligo-vanadates to sarcoplasmic reticulum was analysed by 51V-n.m.r. spectroscopy. The observations indicate that, in addition to monovanadate, the di-, tetra- and deca-vanadates are also bound to sarcoplasmic-reticulum membranes with high affinity. The binding of the vanadate oligoanions may explain some of the effects of vanadates on the conformation and crystallization of Ca2+-transport ATPase.
73 citations
TL;DR: Least-squares refinement of the absorbance data indicates that two anions of sulfate, phosphate, and vanadate bind to each transferrin molecule but that there is detectable binding of only a single bicarbonate anion.
Abstract: The binding of phosphate, bicarbonate, sulfate, and vanadate to human serum transferrin has been evaluated by two difference ultraviolet spectroscopic techniques. Direct titration of apotransferrin with bicarbonate, phosphate, and sulfate produces a strong negative absorbance near 245 nm, while titration with vanadate produces a positive absorbance in this region. Least-squares refinement of the absorbance data indicates that two anions of sulfate, phosphate, and vanadate bind to each transferrin molecule but that there is detectable binding of only a single bicarbonate anion. A second method used to study the thermodynamics of anion binding was competition equilibrium between anions for binding to the transferrin. The equilibrium constant for binding of the first equivalent of vanadate was determined by competition vs. phosphate and sulfate, while the equilibrium constant for binding of the second equivalent of bicarbonate was determined by competition vs. vanadate. Anion binding was described by two equilibrium constants for the successive binding of two anions per transferrin molecule: K1 = [A-Tr]/[A][Tr] and K2 = [A-Tr-A]/[A][A-Tr] where [A] represents the free anion concentration, [Tr] represents apotransferrin concentration, and [A-Tr] and [A-Tr-A] represent the concentrations of 1:1 and 2:1 anion-transferrin complexes, respectively. The results were the following: for phosphate, log K1 = 4.19 +/- 0.03 and log K2 = 3.25 +/- 0.21; for sulfate, log K1 = 3.62 +/- 0.07 and log K2 = 2.79 +/- 0.20; for vanadate, log K1 = 7.45 +/- 0.10 and log K2 = 6.6 +/- 0.30; for bicarbonate, log K1 = 2.66 +/- 0.07 and log K2 = 1.8 +/- 0.3.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: Results indicate that in the normal cross-bridge cycle, inorganic phosphate (Pi) is released from actomyosin before ADP, and the resulting actomyOSin X ADP intermediate can bind Vi and Pi.
Abstract: The suppression of tension development by orthovanadate (Vi) was studied in mechanical experiments and by measuring the binding of radioactive Vi and nucleotides to glycerol-extracted rabbit muscle fibers. During active contractions, Vi bound to the cross-bridges and suppressed tension with an apparent second-order rate constant of 1.34 X 10(3) M-1s-1. The half-saturation concentration for tension suppression was 94 microM Vi. The incubation of fibers in Vi relaxing or rigor solutions prior to initiation of active contractions had little effect on the initial rise of active tension. The addition of adenosine diphosphate (ADP) and Vi to fibers in rigor did not cause relaxation. Suppression of tension only developed during cross-bridge cycling. After slow relaxation from rigor in 1 mM Vi and low (50 microM) MgATP concentration (0 Ca2+), radioactive Vi and ADP were trapped within the fiber. This finding indicated the formation of a stable myosin X ADP X Vi complex, as has been reported in biochemical experiments with isolated myosin. Vi and ADP trapped within the fibers were released only by subsequent cross-bridge attachment. Vi and ADP were preferentially trapped under conditions of cross-bridge cycling in the presence of ATP rather than in relaxed fibers or in rigor with ADP. These results indicate that in the normal cross-bridge cycle, inorganic phosphate (Pi) is released from actomyosin before ADP. The resulting actomyosin X ADP intermediate can bind Vi and Pi. This intermediate probably supports force. Vi behaves as a close analogue of Pi in muscle fibers, as it does with isolated actomyosin.
TL;DR: The experimental results support the conclusion that the H(+) release by roots of intact maize plants is an active process driven by a plasmalemmalocated ATPase.
Abstract: The investigations were focussed on the question as to whether roots of intact maize plants (Zea mays L. cv Blizzard) release protons into deionized H(2)O. Plants in the six to seven leaf stage depressed the pH of deionized H(2)O from 6 to about 4.8 during an experimental period of 4 hours. Only one-third of the protons released could be ascribed to the solvation of CO(2) in H(2)O. The main counter anions released were Cl(-), NO(3) (-), and SO(4) (2-). At low temperature (2 degrees C), the H(+) release was virtually blocked while a relatively high amount of K(+) was released. The presence of K(+), Na(+), Ca(2+), and Mg(2+) in the external solution increased the H(+) secretion significantly. Addition of vanadate to the outer medium inhibited the H(+) release while fusicoccin had a stimulating effect. Substituting the nutrient solution of deionized H(2)O resulted in a substantial increase of the membrane potential difference from -120 to -190 millivolts. The experimental results support the conclusion that the H(+) release by roots of intact maize plants is an active process driven by a plasmalemmalocated ATPase. Since the net H(+) release was not associated with a net uptake of K(+), it is unlikely to originate from a K(+)/H(+) antiport.
TL;DR: When the entire reconstituted vesicle population was treated with ATP and 45Ca in a buffer containing oxalate, the vesicles with Ca2+ transport activity could be separated from other ves Balls by centrifugation in a density gradient and the ATP-dependent Ca2+, transport component was purified approximately 9-fold, indicating that transport-specific fractionation may be used to isolate the ATP+ transport component from liver plasma membrane.
TL;DR: The binding of monovanadate and decavanadate anions to sarcoplasmic reticulum vesicles was measured by equilibrium sedimentation and the affinity of vanadate binding and the molar amount of vanadium bound at equilibrium is much greater with decavan adate than with monovan adate.
Abstract: The binding of monovanadate and decavanadate anions to sarcoplasmic reticulum vesicles was measured by equilibrium sedimentation. The affinity of vanadate binding and the molar amount of vanadium (V) bound at equilibrium is much greater with decavanadate than with monovanadate. The binding data can be rationalized in terms of one binding site per ATPase molecule for monovanadate and two sites per ATPase for decavanadate. The Ca-ATPase crystals formed with monovanadate and with decavanadate are similar in appearance, but decavanadate is particularly effective in promoting the crystallization of Ca2+-ATPase at low V concentration (10-100 microM) in a Ca2+-free medium.
TL;DR: Decavanadate appears to be a non-competitive inhibitor of both hexokinase substrates and phosphofructokinase obtained from bacterial and protistic sources.
TL;DR: Fluorescence analysis and examination of ligand binding and enzymatic properties of the cleaved protein demonstrate that cleavage of the bond stabilizes the E1 form of the protein and abolishes cation exchange and conformational transitions in the protein although binding of cations, nucleotides and phosphate is preserved.
TL;DR: It is shown that the 6-hydroxyl group of glucose is essential for the observed activation by Vi and the formation of glucose 6-vanadate, and the rate of the sulfate-activated glucose oxidation increases linearly with Glu-6-P dehydrogenase concentration, consistent with the proposed mechanism for sulfate activation.
TL;DR: It is indicated that sodium vanadate stimulates bone DNA, collagen, and NCP syntheses in vitro, although high doses of vanadates have an irreversible inhibitory effect.
Abstract: Sodium vanadate, an agent known to have multiple cellular actions, was studied for its effects on aspects of bone formation in cultures of 21-day-old fetal rat calvariae. Vanadate (0.1-10 microM) stimulated the incorporation of [3H] thymidine into acid-insoluble residues (DNA); the effect appeared after 3 h and was sustained for 96 h. Vanadate increased the bone DNA content and mitotic index. Treatment with vanadate at 10 microM for 24 h or at 0.3-1 microM for 96 h increased the incorporation of [3H]proline into collagenase-digestible protein (CDP), but the effect was not specific for collagen; vanadate also increased the labeling of noncollagen protein (NCP). Vanadate increased the incorporation of [3H]proline into type I collagen without affecting other collagen types. Vanadate (100 microM) caused a marked and irreversible inhibitory effect on the labeling of DNA, CDP, and NCP. Treatment with vanadate at multiple doses for 3-96 h did not stimulate alkaline phosphatase activity, but this enzyme was inhibited in bones exposed to 1 mM vanadate for 24 h or 10 microM vanadate for 96 h. The stimulatory effect on DNA labeling was primarily observed in the periosteum, while that on CDP labeling was seen only in the periosteum-free bone. These studies indicate that sodium vanadate stimulates bone DNA, collagen, and NCP syntheses in vitro, although high doses of vanadate have an irreversible inhibitory effect.
TL;DR: Data obtained with vanadate ion support the contention that this enzyme may play a role in the regulation of bone cell growth.
Abstract: Isolated bone cells in culture contain an enzyme capable of hydrolyzing the phosphate ester of phosphotyrosine. This enzyme, which we have termed phosphotyrosine phosphatase, has not previously been reported in bone. Some of its characteristics include: 1) maximum activity near physiological pH, 2) a Km for substrate of 52 microM, 3) marked inhibition by the phosphate analog vanadate ion, 4) activity correlation with bone cell alkaline phosphatase, and 5) regulation by bone target hormones. Data obtained with vanadate ion support the contention that this enzyme may play a role in the regulation of bone cell growth.
TL;DR: The results are consistent with the concept of IP3 serving as a second messenger for insulin secretion, as increases in Ca2+ levels in the submicromolar range have been previously shown to induce insulin release in digitonin-permeabilized islets.
Abstract: Glucose-induced insulin secretion is thought to be mediated by submicromolar increases in intracellular Ca2+, although the intracellular processes are not well understood. We have used the previously characterized digitonin-permeabilized insulin-secreting pancreatic islet model to study the role of myo-inositol 1,4,5-trisphosphate (IP3), a putative second messenger for mobilization of intracellular Ca2+. Ca2+ efflux from the endoplasmic reticulum was studied with or without vanadate present to inhibit Ca2+ reuptake. IP3 (10 microM), at a free Ca2+ level of 0.06 microM, increased Ca2+ release by 30% and, when vanadate was present, by 50%. Maximal and half-maximal Ca2+ release was observed at 10 microM- and 2.5 microM-IP3, respectively. IP3 provoked a rapid release that was followed by slow reuptake. Reuptake was diminished in the presence of vanadate. Inositol 1,4-bisphosphate, inositol 1-phosphate and other phosphoinositide metabolites did not have any significant effect. Because increases in Ca2+ levels in the submicromolar range have been previously shown to induce insulin release in digitonin-permeabilized islets, our results are consistent with the concept of IP3 serving as a second messenger for insulin secretion.
TL;DR: Findings indicate that this membrane preparation is virtually devoid of mitochondrial and tonoplast H(+)-ATPases and Delta pH generation is not inhibited by NO(3) (-).
Abstract: Mg:ATP-dependent H+ pumping has been studied in microsomal vesicles from 24-hour-old radish (Raphanus sativus L.) seedlings by monitoring both intravesicular acidification and the building up of an inside positive membrane potential difference (Δ ψ). ΔpH was measured as the decrease of absorbance of Acridine orange and Δ ψ as the shift of absorbance of bis(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol. Both Mg:ATP-dependent Δ pH and Δ ψ generation are completely inhibited by vanadate and insensitive to oligomycin; moreover, Δ pH generation is not inhibited by NO3−. These findings indicate that this membrane preparation is virtually devoid of mitochondrial and tonoplast H+-ATPases. Both intravesicular acidification and Δ ψ generation are influenced by anions: Δ pH increases and Δ ψ decreases following the sequence SO42−, Cl−, Br−, NO3−. ATP-dependent H+ pumping strictly requires Mg2+. It is very specific for ATP (apparent Km 0.76 millimolar) compared to GTP, UTP, CTP, ITP. Δ pH generation is inhibited by CuSO4 and diethylstilbestrol as well as vanadate. Δ pH generation is specificially stimulated by K+ (+ 80%) and to a lesser extent by Na+ and choline (+28% and +14%, respectively). The characteristics of H+ pumping in these microsomal vesicles closely resemble those described for the plasma membrane ATPase partially purified from several plant materials.
TL;DR: The results suggest that two primary targets exist for vanadate in intact cells: a plasmalemma ATPase which energizes ion uptake and extrusion in Dunaliella and a flagellar ATPase responsible for motility.
TL;DR: It is demonstrated that cholesterol and its oxidized derivatives are able to modulate the calcium channel in human red blood cells in a highly stereospecific manner.
Abstract: To study the effect of cholesterol and its pathophysiologically important oxidized derivatives (OSC) on the calcium entry channel, the human red blood cell was used as a model system. The calcium ejecting adenosinetriphosphatase (ATPase) was inhibited by vanadate. The cells were loaded with OSC at concentrations between 1.25 X 10(-5) and 25 X 10(-5) mol/l. 22-Hydroxycholesterol, cholestan-3 beta,5 alpha,6 beta-triol, 5 alpha-cholestan-3 beta-ol,3 beta,5 alpha-dihydroxycholestan-6-one and 3 beta-hydroxy-5 alpha-cholestan-7-one stimulated 45Ca2+ influx by up to almost 90%, whereas 25-hydroxycholesterol, 7 beta-hydroxycholesterol, 20 alpha-hydroxycholesterol and 7-oxocholesterol inhibited influx by up to 75%. Both stimulation and inhibition were dependent on the amount of OSC incorporated into the membrane. More than 90% of the total modification of calcium influx by OSC was accounted for by an influence on the nitrendipine-inhibitable part of influx. Enrichment of cholesterol in the membrane greatly stimulated, and cholesterol depletion inhibited, Ca2+ influx. These results demonstrate that cholesterol and its oxidized derivatives are able to modulate the calcium channel in human red blood cells in a highly stereospecific manner.
TL;DR: The presence of fluphenazine during the Ca 2+ /CaM-stimulated treatment inhibits membrane phosphorylation and protects the H + -ATPase activity from inhibition.
TL;DR: Cellular vanadium metabolism was studied in Saccharomyces cerevisiae by isolating and characterizing vanadate [VO4(3-), V(V)]-resistant mutants, andVanadate resistance was found to be a recessive trait.
Abstract: Cellular vanadium metabolism was studied in Saccharomyces cerevisiae by isolating and characterizing vanadate [VO4(3-), V(V)]-resistant mutants Vanadate growth inhibition was reversed by the removal of the vanadate from the medium, and vanadate resistance was found to be a recessive trait Vanadate-resistant mutants isolated from glucose-grown cells were divided into five complementation classes containing more than one mutant Among the vanadate-resistant mutants isolated in maltose medium, the majority of mutants were found in only two complementation groups Three of the classes of vanadate-resistant mutants were resistant to 25 mM vanadate but sensitive to 50 mM vanadate in liquid media Two classes of vanadate-resistant mutants were resistant to growth in media containing up to 50 mM vanadate Electron spin resonance studies showed that representative strains of the vanadate-resistant complementation classes contained more cell-associated vanadyl [VO2+, V(IV)] than the parental strains 51 Vanadium nuclear magnetic resonance studies showed that one of the vanadate resonances previously associated with cell toxicity (G R Willsky, D A White, and B C McCabe, J Biol Chem 259:13273-132812, 1984) did not accumulate in the resistant strains compared with the sensitive strain The amount of vanadate remaining in the media after growth was larger for the sensitive strain than for the vanadate-resistant strains All of the strains were able to accumulate phosphate, vanadate, and vanadyl
TL;DR: A cell line originating from the fetal rat aorta has been studied with respect to 45Ca2+ uptake, showing an initial rapid uptake followed by a slow linear phase; both the initial rate and the maximum uptake were increased in the presence of 55 mM potassium chloride.
TL;DR: It is concluded that ATP activation of cathepsin D may play a physiological role in regulation of proteolysis in lysosomes, but that vanadate and molybdate inhibition of lysOSomal proteolyses does not establish ATP dependence.