Topic
Vanadate
About: Vanadate is a research topic. Over the lifetime, 4497 publications have been published within this topic receiving 120109 citations. The topic is also known as: vanadate.
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TL;DR: The catalytic effects suggest that fine tuning of residues Lys-353 and Phe-397, along with addition of negative charge or removal of positive charge near one of the vanadate oxygens, is very important in peroxide activation and halide binding.
79 citations
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TL;DR: The experiments reported here show that in squid axons the ATP-dependent uncoupled Ca efflux can be fully and reversibly inhibited byVanadate, whereas concentrations of vanadate 10 times higher have no effect on the Na–Ca exchange.
Abstract: Nerve cells can maintain a very low intracellular calcium concentration ([Ca2+]i) against large Ca2+ electrochemical gradients (see ref. 1 for review). The properties of the calcium efflux from these cells depend on [Ca2+]i (ref. 2), and within the physiological range, most Ca efflux depends on ATP (which stimulates with high affinity) and is insensitive to Nai, Na0 and Ca0 (uncoupled Ca efflux). When the [Ca2+]i is well above the physiological range, Ca efflux becomes only partially dependent on ATP (acting now with low affinity), is inhibited by Nai and is stimulated by Na0 and Ca0 (Na–Ca exchange). Orthovanadate, a powerful inhibitor of the (Na++K+) ATPase and the Na pump3,4, also inhibits the Ca-stimulated ATPase activity, which is the enzymatic basis for the uncoupled Ca pump, in human red cells5. The experiments reported here show that in squid axons the ATP-dependent uncoupled Ca efflux can be fully and reversibly inhibited by vanadate, whereas concentrations of vanadate 10 times higher have no effect on the Na–Ca exchange. This is another indication that the uncoupled Ca efflux represents an ATP-driven Ca pump, and supports the suggestion that the uncoupled Ca efflux and Na–Ca exchange are mediated by different mechanisms2.
79 citations
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TL;DR: The glucose-lowering effect of vanadate in STZ-induced diabetic rats can be explained by its inhibition of feeding, and its hypophagic action does not appear to involve inhibition of NPYergic pathways in the hypothalamus.
Abstract: Vanadate treatment can lower glycemia in diabetic rats. This action is generally attributed to vanadate's insulinomimetic properties, but vanadate also inhibits feeding, which could lower blood glucose. We therefore assessed the contribution of hypophagia to vanadate's antihyperglycemic action in a 3-week study of streptozocin-induced (STZ) diabetic rats. Untreated diabetic rats ( n = 8) ate 54% more food than nondiabetic control rats ( P 0.05 vs. vanadate-treated diabetic rats). Vanadate treatment did not affect plasma insulin concentrations in diabetic rats. In nondiabetic rats ( n = 8), vanadate treatment significantly reduced food intake ( P < 0.05) and also lowered plasma insulin concentrations ( P < 0.05) without significantly affecting glycemia. To investigate the mechanism of vanadate's hypophagic effect, we also measured regional hypothalamic levels of neuropeptide Y (NPY), a potent central appetite stimulant that is thought to drive hyperphagia in STZ-induced diabetes. Hypothalamic NPY concentrations rise markedly in diabetes and are normalized by insulin replacement. Unlike insulin, vanadate treatment did not normalize regional hypothalamic NPY concentrations in diabetic rats. Vanadate does not therefore appear to exert an insulin-like action at the hypothalamic level; its hypophagic action does not appear to involve inhibition of NPYergic pathways in the hypothalamus. We conclude that the glucose-lowering effect of vanadate in STZ-induced diabetic rats can be explained by its inhibition of feeding. Although vanadate has certain insulinomimetic effects in vitro and in vivo, the role of these effects in vanadate's antidiabetic actions must be critically reexamined.
79 citations
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TL;DR: Two Ca2+-transport systems resembled, respectively, the sarcolemmal and sarcoplasmic reticulum Ca1+ pumps in cardiac and skeletal muscle, in accordance with the subcellular locations established by density gradient centrifugation.
79 citations
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TL;DR: The data indicate that a cytosolic free Ca2+ concentration of 4 X 10(-7) mol/l can be regulated in pancreatic acinar cells by a nonmitochondrial Mg2+-dependent Ca2-dependent pool.
Abstract: Ca2+ uptake into isolated exocrine pancreatic cells with highly permeable plasma membrane was determined by measuring the decrease in free Ca2+ concentration of the surrounding incubation medium with a Ca2+-specific electrode. In the presence of Mg-ATP and respiratory substrates the free Ca2+ concentration of the incubation medium decreased rapidly after addition of leaky cells until a stable medium free Ca2+ concentration of 4.2 +/- 0.1 X 10(-7) mol/l was obtained. Changes in the medium free Ca2+ concentration at steady state by addition of Ca2+ or EGTA were buffered by cellular uptake or release, respectively, until the steady-state free Ca2+ concentration was reestablished. When nonmitochondrial Ca2+ uptake was determined in the presence of a combination of mitochondrial inhibitors (10(-5) mol/l antimycin, 5 X 10(-6) mol/l oligomycin, and 10(-2) mol/l azide), the rate of uptake was considerably reduced, while the steady-state concentration was unaltered. In contrast, mitochondrial uptake that could be observed in the presence of the ATPase inhibitor vanadate (2 X 10(-3) mol/l) proceeded at the same rate as the control, but the minimal medium free Ca2+ concentration reached was 2.4 +/- 0.1 X 10(-7) mol/l higher than the control. Addition of secretagogues at steady-state free Ca2+ concentration resulted in a Ca2+ release of 0.73 +/- 0.08 nmol/mg protein. The increase in medium free Ca2+ concentration was entirely transient and followed by reuptake to the prestimulation level. The data indicate that a cytosolic free Ca2+ concentration of 4 X 10(-7) mol/l can be regulated in pancreatic acinar cells by a nonmitochondrial Mg2+-dependent Ca2+ pool.
78 citations