Stimulation of glucose transport in rat adipocytes by calcium

1979 ◽  
Vol 57 (6) ◽  
pp. 692-699 ◽  
Author(s):  
Wayne M. Taylor ◽  
Lena Hau ◽  
Mitchell L. Halperin
Keyword(s):  
Glucose Transport ◽  
Maximum Velocity ◽  
Pentose Phosphate ◽  
Calcium Flux ◽  
Intracellular Camp ◽  
Rat Adipocytes ◽  
Phosphorylation Mechanism ◽  
Rate Limiting ◽  
Camp Levels ◽  
Stimulation Of

Glucose transport in rat adipocytes was studied by monitoring the conversion of [1-14C]-glucose to 14CO2 in a system where glucose transport was made rate-limiting by increasing the flux through the pentose phosphate pathway with phenazine methosulphate, an agent which rapidly reoxidizes NADPH. Calcium increased both basal and insulin-stimulated apparent rates of glucose transport by approximately 40%. The maximum velocity of the apparent rate of glucose transport was increased by extracellular calcium both in the presence or absence of insulin. There was no change in the glucose concentration required for half-maximal rates of 14CO2 production. Calcium also enhanced the stimulation of apparent rates of glucose transport by insulin when examined over a range of hormone concentrations. Adipocyte cAMP concentrations were significantly lowered by calcium under conditions which led to increased apparent rates of glucose transport. In contrast, cobalt and nickel, antagonists of calcium action, elevated adipocyte cAMP levels and inhibited apparent rates of glucose transport. Agents which inhibit transmembrane calcium flux (verapamil, tetracaine, and procaine) inhibited apparent rates of glucose transport despite a reduction in adipocyte cAMP concentration.On the basis of the above data we suggest that calcium may increase apparent rates of glucose transport in rat adipocytes both by lowering intracellular cAMP concentration and by a further mechanism independent of changes in the level of cAMP. These results are consistent with the hypothesis that glucose transport in rat adipocytes may be controlled, in part, by a cAMP-induced phosphorylation mechanism.

Control of glucose transport in adipose tissue of the rat: Role of insulin, ATP, and intracellular metabolites

1978 ◽  
Vol 56 (7) ◽  
pp. 708-712 ◽  
Author(s):  
Mitchell L. Halperin ◽  
Marina L. Mak ◽  
Wayne M. Taylor
Keyword(s):  
Adipose Tissue ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Maximum Velocity ◽  
Pentose Phosphate ◽  
Maximal Velocity ◽  
Rate Limiting ◽  
Phenazine Methosulphate ◽  
Intracellular Glucose

The purpose of this study was to elucidate some of the mechanisms of control of the glucose transport step in adipose tissue. Glucose transport was studied by monitoring the conversion of [1-14C]glucose to 14CO2 in a system where glucose transport was made rate limiting by increasing the flux through the pentose phosphate pathway with phenazine methosulphate, an agent which results in rapid rates of reoxidation of NADPH. The maximum velocity for the apparent rate of glucose transport was increased significantly by insulin. There was no change in the glucose concentration required for half-maximal rates of 14CO2 production. Glucose transport was also monitored by directly measuring the rate of glucose uptake. Glucose uptake was increased by phenazine methosulphate. The intracellular glucose-6-phosphate concentration was decreased by phenazine methosulphate. These two agents, insulin and phenazine methosulphate, seemed to act by independent mechanisms as their optimal effects on glucose uptake were additive.The apparent rate of glucose transport was decreased by ATP which resulted in a decrease in maximal velocity but did not affect the affinity for glucose. This effect of ATP was seen in the presence or absence of insulin.

scholarly journals Stimulation of glucose transport in rat adipocytes by insulin, adenosine, nicotinic acid and hydrogen peroxide. Role of adenosine 3′:5′-cyclic monophosphate

1979 ◽  
Vol 178 (2) ◽  
pp. 381-389 ◽  
Author(s):  
Wayne M. Taylor ◽  
Mitchell L. Halperin
Keyword(s):  
Cyclic Amp ◽  
Nicotinic Acid ◽  
Glucose Transport ◽  
Pentose Phosphate ◽  
High Cell ◽  
Stimulatory Action ◽  
Rat Adipocytes ◽  
Cell Concentrations ◽  
Stimulation Of

Glucose transport into adipocytes of the rat was measured by monitoring the conversion of [1-14C]glucose into 14CO2. Glucose transport was made rate-limiting by increasing the flux through the pentose phosphate pathway with phenazine methosulphate, an agent that rapidly reoxidizes NADPH. Under these conditions, the observed rate of glucose disappearance from the incubation medium was about 20% higher than the rate of conversion of the C-1 of glucose into 14CO2. Apparent rates of glucose transport were significantly increased by insulin, H2O2, adenosine and nicotinic acid. Stimulation of the apparent rate of glucose transport by insulin was dependent on adipocyte concentration, the hormone being most effective at relatively high cell concentrations. Adenosine and nicotinic acid further enhanced the maximum stimulation of glucose transport by insulin. Potentiation of insulin action by adenosine was more pronounced at lower cell concentrations. At relatively high cell concentrations the stimulatory action of insulin was markedly decreased by adenosine deaminase. Stimulation of apparent rates of glucose transport by the compounds noted above were antagonized by agents that increased intracellular cyclic AMP concentrations (theophylline and isoprenaline) and by dibutyryl cyclic AMP. Intracellular concentrations of cyclic AMP were significantly lowered when adipocytes were incubated with insulin, H2O2, adenosine or nicotinic acid. These effects were observed under basal conditions or when intracellular cyclic AMP concentrations were elevated by theophylline or isoprenaline. On the basis of the above data, we suggest that insulin, H2O2, adenosine and nicotinic acid may all stimulate glucose transport in rat adipocytes by lowering the intracellular cyclic AMP concentration. These data therefore support the hypothesis that cyclic AMP inhibits glucose transport in rat adipocytes.

scholarly journals Stimulation of a glycosyl-phosphatidylinositol-specific phospholipase by insulin and the sulfonylurea, glimepiride, in rat adipocytes depends on increased glucose transport.

1994 ◽  
Vol 126 (5) ◽  
pp. 1267-1276 ◽  
Author(s):  
G Müller ◽  
E A Dearey ◽  
A Korndörfer ◽  
W Bandlow
Keyword(s):  
Glucose Transport ◽  
Inositol Phosphate ◽  
Glycosyl Phosphatidylinositol ◽  
Cyclic Monophosphate ◽  
Rat Adipocytes ◽  
Residual Protein ◽  
Adipocyte Cell ◽  
Anchor Structure ◽  
Specific Insulin ◽  
Stimulation Of

Lipoprotein lipase (LPL) and glycolipid-anchored cAMP-binding ectoprotein (Gce1) are modified by glycosyl-phosphatidylinositol (GPI) in rat adipocytes, however, the linkage is potentially unstable. Incubation of the cells with either insulin (0.1-30 nM) or the sulfonylurea, glimepiride (0.5-20 microM), in the presence of glucose led to conversion of up to 35 and 20%, respectively, of the total amphiphilic LPL and Gce1 to their hydrophilic versions. Inositol-phosphate was retained in the residual protein-linked anchor structure. This suggests cleavage of the GPI anchors by an endogenous GPI-specific insulin- and glimepiride-inducible phospholipase (GPI-PL). Despite cleavage, hydrophilic LPL and Gce1 remained membrane associated and were released only if a competitor, e.g., inositol-(cyclic)monophosphate, had been added. Other constituents of the GPI anchor (glucosamine and mannose) were less efficient. This suggests peripheral interaction of lipolytically cleaved LPL and Gce1 with the adipocyte cell surface involving the terminal inositol-(cyclic)monophosphate epitope and presumably a receptor of the adipocyte plasma membrane. In rat adipocytes which were resistant toward glucose transport stimulation by insulin, the sensitivity and responsiveness of GPI-PL to stimulation by insulin was drastically reduced. In contrast, activation of both GPI-PL and glucose transport by the sulfonylurea, glimepiride, was not affected significantly. Inhibition of glucose transport or incubation of rat adipocytes in glucose-free medium completely abolished stimulation of GPI-PL by either insulin or glimepiride. The activation was partially restored by the addition of glucose or nonmetabolizable 2-deoxyglucose. These data suggest that increased glucose transport stimulates a GPI-PL in rat adipocytes.

scholarly journals Adenosine 3':5'-monophosphate content and actions in the division cycle of synchronized HeLa cells.

1976 ◽  
Vol 71 (2) ◽  
pp. 515-534 ◽  
Author(s):  
C E Zeilig ◽  
R A Johnson ◽  
E W Sutherland ◽  
D L Friedman
Keyword(s):  
Cell Cycle ◽  
Cyclic Amp ◽  
Hela Cells ◽  
S Phase ◽  
Intracellular Camp ◽  
Specific Effects ◽  
Low Concentrations ◽  
High Concentrations ◽  
Camp Levels ◽  
Stimulation Of

The involvement of adenosine 3':5'-monophosphate (cAMP) in the regulation of the cell cycle was studied by determining intracellular fluctuations in cAMP levels in synchronized HeLa cells and by testing the effects of experimentally altered levels on cell cycle traverse. Cyclic AMP levels were lowest during mitosis and were highest during late G-1 or early S phase. These findings were supported by results obtained when cells were accumulated at these points with Colcemid or high levels of thymidine. Additional fluctuations in cAMP levels were observed during S phase. Two specific effects of cAMP on cell cycle traverse were found. Elevation of cAMP levels in S phase or G-2 caused arrest of cells in G-2 for as long as 10 h and lengthened M. However, once cells reached metaphase, elevation of cAMP accelerated the completion of mitosis. Stimulation of mitosis was also observed after addition of CaCl2. The specificity of the effects of cAMP was verified by demonstrating that: (a) intracellular cAMP was increased after exposure to methylisobutylxanthine (MIX) before any observed effects on cycle traverse; (b) submaximal concentrations of MIX potentiated the effects of isoproterenol; and (c) effects of MIX and isoproterenol were mimicked by 8-Br-cAMP. MIX at high concentrations inhibited G-1 traverse, but this effect did not appear to be mediated by cAMP. Isoproterenol slightly stimulated G-1 traverse and partially prevented the MIX-induced delay. Moreover, low concentrations of 8-Br-cAMP (0.10-100 muM) stimulated G-1 traverse, whereas high concentrations (1 mM) inhibited. Both of these effects were also observed with the control, Br-5'-AMP, at 10-fold lower concentrations.

Stimulatory effect of lithium on glucose transport in rat adipocytes is not mediated by elevation of IP1

1998 ◽  
Vol 275 (2) ◽  
pp. E272-E277 ◽  
Author(s):  
Xiaoli Chen ◽  
Ellen G. McMahon ◽  
Eric A. Gulve
Keyword(s):  
Glucose Uptake ◽  
Glucose Transport ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Transport Activity ◽  
Concentration Dependent Manner ◽  
Inositol 1 ◽  
Rat Adipocytes ◽  
Increase Glucose Uptake ◽  
Stimulation Of

Lithium has been shown to increase glucose uptake in skeletal muscle and adipose tissues. The therapeutic effect of lithium on bipolar disease is thought to be mediated by its inhibitory effect on myo-inositol-1-monophosphatase (IMPase). We tested the hypothesis that the stimulatory effect of lithium on glucose uptake results from inhibition of IMPase and the resultant accumulation of inositol monophosphates (IP1) by comparing the effects of lithium and a selective IMPase inhibitor, L-690,488, on isolated rat adipocytes. Insulin produced a concentration-dependent stimulation of 2-deoxy-d-[14C]glucose (2-DG) transport (10 μU/ml caused half-maximal activation). Acute exposure to lithium stimulated basal glucose transport activity in a concentration-dependent manner, with a threefold stimulation at 30 mM lithium. Lithium also potentiated insulin-stimulated 2-DG transport. Lithium produced a concomitant increase in IP1 accumulation. In contrast, L-690,488 increased IP1 to levels comparable to those of lithium without stimulatory effects on 2-DG transport. These results demonstrate that stimulatory effects of lithium on glucose transport are not mediated by the inhibition of IMPase and subsequent accumulation of IP1 in rat adipocytes.

Sign in / Sign up

Export Citation Format

Share Document