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.

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.

Renal metabolism of N6,O2'-dibutyryl adenosine 3',5'-monophosphate

1979 ◽  
Vol 237 (1) ◽  
pp. F75-F84
Author(s):  
R. Coulson ◽  
W. W. Harrington
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Urinary Excretion ◽  
Rat Kidney ◽  
Bond Cleavage ◽  
Dibutyryl Cyclic Amp ◽  
Renal Metabolism ◽  
Phosphate Bond ◽  
Isolated Rat

Metabolism of dibutyryl cyclic AMP was studied by including the 3H- or C-labeled nucleotide (0.1 mM, 5 mumol) in the recirculating perfusate of the isolated rat kidney. Kidneys were perfused with nucleotide for 60 min. Dibutyryl cyclic AMP was almost completely cleared from the perfusate, about one-quarter as urinary excretion principally by probenecid-sensitive secretion and about one-half as metabolism beyond 3'-phosphate bond cleavage. The principal metabolite, N6-monobutyryl adenosine, accounted for one-third of added dibutyryl cyclic AMP. The remaining metabolites were ATP, ADP AMP, and N6-monobutyryl AMP. Dibutyryl cyclic AMP (0.1 or 1.0 mM) elevated renal ATP but did not alter uricogenesis. Both dibutyryl cyclic AMP and cyclic AMP at 0.2 mM produced similar activation and subcellular redistribution of renal protein kinase. N6-monobutyryl adenosine, unlike adenosine, had no effect on the renal activity of adenylate cyclase, low Km cyclic AMP phosphodiesterase, and protein kinase. Dibutyryl cyclic AMP is like exogenous cyclic AMP in that it penetrates the rat kidney, activates protein kinase, and is metabolized to ATP (R. Coulson, J. Biol. Chem. 251: 4958-4967, 1976), but is unlike cyclic AMP in its extent of secretion and metabolism to ATP and urate and in its formation of the unique metabolites N6-monobutyryl AMP and N6-monobutyryl adenosine.

scholarly journals Factors regulating the production of prostaglandin E2 and prostacyclin (prostaglandin I2) in rat and human adipocytes

1987 ◽  
Vol 247 (2) ◽  
pp. 389-394 ◽  
Author(s):  
B Richelsen
Keyword(s):  
Angiotensin Ii ◽  
Cyclic Amp ◽  
Prostaglandin E2 ◽  
Acetylsalicylic Acid ◽  
Dependent Manner ◽  
Human Adipocytes ◽  
Prostaglandin I2 ◽  
Concentration Dependent Manner ◽  
Rat Adipocytes ◽  
Isolated Adipocytes

The regulation of PGE2 (prostaglandin E2) and PGI2 (prostaglandin I2; prostacyclin) formation was investigated in isolated adipocytes. The formation of both PGs was stimulated by various lipolytic agents such as isoproterenol, adrenaline and dibutyryl cyclic AMP. During maximal stimulation the production of PGE2 and PGI2 (measured as 6-oxo-PGF1 alpha) was 0.51 +/- 0.04 and 1.21 +/- 0.09 ng/2 h per 10(6) cells respectively. Thus PGI2 was produced in excess of PGE2 in rat adipocytes. The production of the PGs was inhibited by indomethacin and acetylsalicylic acid in a concentration-dependent manner. The half-maximal effective concentration of indomethacin was 328 +/- 38 nM and that of acetylsalicylic acid was 38.5 +/- 5.3 microM. The PGs were maximally inhibited by 70-75% after incubation for 2 h. In contrast with their effect on PG production, the two agents had a small potentiating effect on the stimulated lipolysis (P less than 0.05). The phospholipase inhibitors mepacrine and chloroquine inhibited both PG production and triacylglycerol lipolysis and were therefore unable to indicate whether the PG precursor, arachidonic acid, originates from phospholipids or triacylglycerols in adipocytes. Angiotensin II significantly (P less than 0.05) stimulated both PGE2 and PGI2 production in rat adipocytes without affecting triacylglycerol lipolysis. Finally, it was shown that PGE2 and PGI2 were also produced in human adipocytes, although in smaller quantities than in rat adipocytes. It is concluded that the production of PGs in isolated adipocytes is regulated by various hormones. Moreover, at least two separate mechanisms for PG production may exist in adipocytes: (1) a mechanism that is activated concomitantly with triacylglycerol lipolysis (and cyclic AMP) and (2) an angiotensin II-sensitive, but lipolysis (and cyclic AMP)-independent mechanism.

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 Different modulatory effects of elevated cyclic AMP on cytosolic Ca2+ spikes induced by phenylephrine or vasopressin in single rat hepatocytes

1993 ◽  
Vol 291 (1) ◽  
pp. 163-168 ◽  
Author(s):  
A Sanchez-Bueno ◽  
I Marrero ◽  
P H Cobbold
Keyword(s):  
Cyclic Amp ◽  
Rat Hepatocytes ◽  
Specific Information ◽  
Dibutyryl Cyclic Amp ◽  
Isolated Rat Hepatocytes ◽  
Frequency Peak ◽  
Isolated Rat

We show here, by aequorin measurements in single isolated rat hepatocytes, that elevation of cyclic AMP, by dibutyryl cyclic AMP, forskolin or glucagon, has different effects on oscillations in cytosolic concentration of free Ca2+ (‘free Ca’) induced by phenylephrine or vasopressin. Elevated cyclic AMP does not itself induce free Ca oscillations, but enhances both the peak free Ca and the frequency of spikes induced by phenylephrine. In contrast, elevated cyclic AMP has no effect on peak free Ca of vasopressin-induced spikes, but markedly prolongs the falling phase, with the result that spiking frequency (peak to peak) falls, although the period between spikes of resting free Ca is usually decreased. The data provide another example of receptor-specific information being retained in the oscillator mechanism, with implications for models of the hepatocyte calcium oscillator.

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