scholarly journals Insulin-like effects of dithiothreitol on isolated rat adipocytes

1981 ◽  
Vol 200 (2) ◽  
pp. 425-428 ◽  
Author(s):  
H Goko ◽  
S Takashima ◽  
A Kawamuro ◽  
A Matsuoka
Keyword(s):  
Glucose Oxidation ◽  
Insulin Receptors ◽  
Insulin Binding ◽  
Dibutyryl Cyclic Amp ◽  
Rat Adipocytes ◽  
Adrenergic Antagonist ◽  
Isolated Adipocytes ◽  
Dose Dependent ◽  
Isolated Rat ◽  
Stimulation Of

The effects of dithiothreitol on basal glucose oxidation, hormone-induced lipolysis and insulin receptors in isolated rat adipocytes were studied. Dithiothreitol produced a dose-dependent stimulation of basal glucose oxidation and inhibition of adrenaline-induced lipolysis. Dithiothreitol also inhibited corticotropin-induced lipolysis, but failed to inhibit dibutyryl cyclic AMP-induced lipolysis. Dithiothreitol did not inhibit the binding of the beta-adrenergic antagonist [3H]dihydroalprenolol to adipocytes. Neither catalase (100 micrograms/ml) nor EDTA (2 mM) abolished the antilipolytic effect of dithiothreitol. Treatment of isolated adipocytes with 1 mM-dithiothreitol for 20 min at 37 degrees C also caused stimulation of basal glucose oxidation and inhibition of adrenaline-induced lipolysis. A Scatchard plot of insulin binding to control adipocytes was curvilinear. However, treatment of cells with 1 mM-dithiothreitol decreased the curvilinearity of the plot, indicating that only a low-affinity state of the insulin receptors exists in the dithiothreitol-treated adipocytes. These findings suggest that the insulin-like activities of dithiothreitol are mediated through the interaction of dithiothreitol with insulin receptors.

scholarly journals Tumour-promoting phorbol esters increase basal and inhibit insulin-stimulated lipogenesis in rat adipocytes without decreasing insulin binding

1985 ◽  
Vol 225 (2) ◽  
pp. 523-527 ◽  
Author(s):  
G van de Werve ◽  
J Proietto ◽  
B Jeanrenaud
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Insulin Action ◽  
Phorbol Esters ◽  
Insulin Binding ◽  
Rat Adipocytes ◽  
Kinase C ◽  
Dose Dependent ◽  
Isolated Rat ◽  
Stimulation Of

In isolated rat adipocytes, tumour-promoting phorbol esters caused (1) dose-dependent stimulation of lipogenesis in the absence of insulin and (2) inhibition of the lipogenic effect of submaximal concentrations of insulin, but without affecting insulin binding. The possible involvement of protein kinase C in insulin action is discussed.

Regulation of glucose transport in isolated adipocytes by levamisole

1992 ◽  
Vol 70 (8) ◽  
pp. 1190-1194 ◽  
Author(s):  
Nirmal S. Basi ◽  
K. G. Thomaskutty ◽  
Richard H. Pointer
Keyword(s):  
Glucose Transport ◽  
Glucose Oxidation ◽  
Glucose Utilization ◽  
Rat Adipocytes ◽  
Phosphofructokinase Activity ◽  
Isolated Adipocytes ◽  
Isolated Rat

When isolated rat adipocytes were incubated with increasing concentrations of levamisole (0.5–5 mM), basal glucose oxidation decreased by almost 50% and insulin-stimulated glucose oxidation decreased by 90%. The decrease in glucose oxidation correlated with an inhibition of glucose transport, since levamisole at 5.0 mM decreased basal 3-O-methylglucose transport by 60% and insulin-stimulated transport by 80%. Diamide-stimulated glucose transport was also inhibited approximately 80% by 5.0 mM levamisole. Levamisole at concentrations up to 5.0 mM had no effect on phosphofructokinase activity. The present results suggest that levamisole inhibits glucose utilization by inhibiting glucose transport in a concentration-dependent manner.Key words: insulin, levamisole, glucose transport, adipocytes.

scholarly journals Catecholamine-induced insulin resistance of glucose transport in isolated rat adipocytes

1983 ◽  
Vol 216 (3) ◽  
pp. 737-745 ◽  
Author(s):  
D M Kirsch ◽  
M Baumgarten ◽  
T Deufel ◽  
F Rinninger ◽  
W Kemmler ◽  
...  
Keyword(s):  
Glucose Transport ◽  
Insulin Binding ◽  
Affinity Binding ◽  
Insulin Stimulation ◽  
High Affinity Binding ◽  
Rat Adipocytes ◽  
High Affinity ◽  
Atp Levels ◽  
Isolated Rat ◽  
Stimulation Of

The effects of pre-incubation with isoprenaline and noradrenaline on insulin binding and insulin stimulation of D-glucose transport in isolated rat adipocytes are reported. (1) Pre-incubation of the cells with isoprenaline (0.1-10 microM) in Krebs-Ringer-Hepes [4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid] buffer (30 min, 37 degrees C) at D-glucose concentrations of 16 mM, in which normal ATP levels were maintained, caused a rightward-shift in sensitivity of D-glucose transport to insulin stimulation by 50% and a decrease in maximal responsiveness by 30% (2) [A14-125I]insulin binding was reduced significantly by 35% at insulin concentrations less than 100 mu-units/ml and Scatchard analysis showed that this consisted mainly of a decrease in high-affinity binding. (3) Pre-incubation with catecholamines under the same conditions but at low glucose concentrations (0-5 mM) caused a fall in intracellular ATP levels of 65 and 45% respectively. (4) The fall in ATP additionally lowered insulin binding by 50% at all insulin concentrations and a parallel shift of the binding curves in the Scatchard plot showed that this was due to a decrease in the number of receptors. (5) At low and high ATP concentrations the insulin stimulation of D-glucose transport was inhibited to a similar extent. (6) Pre-incubation with catecholamines thus inhibited insulin stimulation of D-glucose transport in rat adipocytes mainly by a decrease in high-affinity binding of insulin, which was not mediated by low ATP levels. This mechanism may play a role in the pathogenesis of catecholamine-induced insulin resistance in vivo.

scholarly journals Characterization of antilipolytic action of polyamines in isolated rat adipocytes

1989 ◽  
Vol 261 (2) ◽  
pp. 661-665 ◽  
Author(s):  
B Richelsen ◽  
S B Pedersen ◽  
D M Hougaard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Concentration ◽  
Dibutyryl Cyclic Amp ◽  
Physiological Regulation ◽  
Rat Adipocytes ◽  
Pde Inhibitors ◽  
Isolated Adipocytes ◽  
Lipolytic System ◽  
Isolated Rat

The interactions of polyamines with the lipolytic system were studied in isolated rat adipocytes. Spermine, spermidine and putrescine significantly inhibited adenosine deaminase-stimulated lipolysis. An antilipolytic effect of spermine was detectable at a concentration of 0.25 mM (P less than 0.05). At a concentration of 10 mM all three polyamines inhibited the stimulated lipolysis by 50-60% (P less than 0.001). In addition, spermine enhanced the antilipolytic sensitivity of insulin. Spermine (1 mM) decreased the half-maximal inhibitory concentration of insulin from 320 +/- 70 pM to 56 +/- 20 pM (P less than 0.01). The antilipolytic effects and the cyclic-AMP-lowering effects of the polyamines were almost completely prevented in the presence of different phosphodiesterase (PDE) inhibitors (3-isobutyl-1-methylxanthine and RO 20-1724) and, in addition, polyamines had no effect on lipolysis stimulated by dibutyryl cyclic AMP, indicating that polyamines may inhibit lipolysis by activating the PDE enzyme. This latter suggestion was confirmed by demonstrating that spermine (5 mM) significantly enhanced the low-Km PDE enzyme activity (P less than 0.01). Finally, the amounts of polyamines present in isolated adipocytes were measured, and the estimated cytoplasmic concentrations were 0.02 mM (putrescine), 0.86 mM (spermidine), and 1.0 mM (spermine). It is concluded that polyamines may possibly be involved in the physiological regulation of triacylglycerol mobilization in adipocytes.

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