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We have examined the effects of extracellular and intracellular Ca2+ concentrations upon basal and insulin-stimulated 2-deoxyglucose uptake in isolated rat adipocytes. In the absence of extracellular Ca2+, both basal and insulin-stimulated glucose uptake were significantly reduced. Insulin-stimulated glucose transport was optimal at 1 and 2 mM Ca2+. Further(More)
We examined Na(+)-K(+)-ATPase activity and the levels of alpha I-, alpha II-, and beta-subunit mRNA and protein in aortic cells of diabetic rats. Diabetes was induced by streptozocin. Na(+)-K(+)-ATPase activity was significantly reduced on the 2nd day of diabetes (9.4 +/- 1.3 vs. 17.5 +/- 2.1 mumol NADH.mg-1 protein.h-1, P less than 0.05) and remained(More)
Insulin- and glyburide-stimulated changes in cytosolic free calcium concentrations [( Ca2+]i) were studied in gluteal adipocytes obtained from six obese women (139 +/- 3% ideal body wt) and six healthy, normal weight age- and sex-matched controls. Biopsies were performed after an overnight fast and twice (at 3 and 6 h) during an insulin infusion (40 mU/m2(More)
In this study, we examined the influence of high levels of cytosolic calcium on phosphorylation status and function of GLUT-4 in isolated rat adipocytes. Intracellular calcium was elevated by exposing adipocytes to either extracellular ATP (1.6 mM) or thapsigargin (100 nM). Both agents increased cytosolic calcium 2-3 fold. While basal glucose uptake was(More)
In this study, we examined the mechanism of inhibition of phosphoserine phosphatase (PSPase) activity by elevated [Ca2+]i in insulin target cells. In in vitro studies, isolated rat adipocytes were incubated with either 40 mM K+ or parathyroid hormone (PTH) (20 ng/ml) for 1 h. In in vivo studies, rats were injected with PTH (three hourly injections of 40(More)
Concomitant with glucose-induced insulin release, there occurred an increase of ATP from 4.40 plus or minus 0.21 to 23.16 plus or minus 0.52 pmol/100 islets/min (P less than 0.001) in the effluent from perifused rat islets. There is a linear relationship between circulating ATP and insulin levels both in the stimulated and basal state (r = 0.689, P less(More)
Exogenous arachidonic acid does not stimulate insulin release in Ca++-containing medium, but a potent effect was unmasked by extracellular Ca++ depletion. This secretion met several criteria of exocytotic release. It did not require the oxygenation of arachidonate or its esterification into islet membranes, but was potentiated by the presence of 16.7 mM(More)
We evaluated the possible relationship between [Ca2+]i and glucose uptake in the postabsorptive state and postprandially in adipocytes obtained from normal and obese subjects, as well as from patients with non-insulin-dependent diabetes mellitus (NIDDM). Adipocytes isolated from overnight-fasted obese and NIDDM patients revealed high levels of [Ca2+]i (p(More)