WORTMANNIN CONVERTS INSULIN BUT NOT OXYTOCIN FROM AN ANTILIPOLYTIC TOA LIPOLYTIC AGENT IN THE PRESENCE OF FORSKOLIN

Insulin is an important regulator of glucose transport and lipolysis i n adipocytes, The present studies compared the effects of insulin in r at adipocytes with the effects of oxytocin and peroxovanadate, which m imic some effects of insulin. The antilipolytic effects of peroxovanad ate and oxytocin were unaffected by 500 nmol/L wortmannin, which block ed the antilipolytic action of insulin, However, wortmannin, which is a relatively specific inhibitor of phosphatidylinositol 3-kinase, did block most of the stimulation of glucose metabolism by peroxovanadate while having little effect on that due to oxytocin, Under appropriate conditions, it was also possible to demonstrate a lipolytic action of insulin, especially with low (0.1 to 1 nmol/L) concentrations of insul in after exposure of adipocytes to 50 nmol/L wortmannin, The data prov ide additional support for the hypothesis that oxytocin and peroxovana date affect adipose tissue metabolism by mechanisms distinctly differe nt from those involved in insulin action. Copyright (C) 1997 by W.B. S aunders Company