Effect of partially purified NSILA on adenylate cyclase, phosphodiesterase and 3',5'-cyclic AMP in fat cells.
Partially purified, non-suppressible, insulin-like material (NSILA-S)  was studied with respect to its effect on the levels of 3',5'-cyclic adenosine monophosphate (cAMP) and its mechanism of action in the control of this nucleotide in rat fat cells. NSILA-S prevents the rise of cAMP in fat cells under the influence of isoproterenol with similar kinetics to insulin. A maximal effect is observed at about 70 ng/ml with a biological activity equivalent to 200 muU/ml of insulin. NSILA-S inhibits norepinephrine-stimulated adenylate cyclase activity in fat cell ghosts and partially purified plasma membrane preparations. At 10 mM Mg2+, the inhibition is characterized by an effect of Vmax without change in affinity towards ATP (apparent KM 30 muM). Similarly there is no observed change in affinity towards Mg2+. With respect to inhibition of norepinephrine-stimulated adenylate cyclase, the dose-response curve of NSILA-S is similar to that already found with intact cells. The effect of norepinephrine is inhibited throughout the dose-response range between 5 X 10(-7) and 5 X 10(-4) M. In contrast to previous observations with insulin in ghosts, NSILA-S inhibits the basal adenylate cyclase activity. Cyclic nucleotide phosphodiesterase activity in homogenates as measured at 1.0 muM substrate is increased by 90% after previous incubation of fat cells with NSILA-S. The study suggests that the anti-lipolytic effect of NSILA-S is mediated by a lowering of cAMP through inhibition of the adenylate cyclase and/or stimulation of the phosphodiesterase system.
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000273:Adipose Tissue / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D001798:Blood Proteins / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D000242:Cyclic AMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D007328:Insulin / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D051381:Rats
D001798:Blood Proteins; D007328:Insulin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D000262:Adenylyl Cyclases; D008274:Magnesium; D007545:Isoproterenol; D009638:Norepinephrine