Hormonal regulation of lipolysis and phosphorylase activity in human fat cells

Abstract

Prostaglandin E₁ (PGE₁) at a concentration of 1 ng/ml antagonized theophylline, and norepinephrine induced release of glycerol and free fatty acids (FFA) in human fat cell preparations. Insulin at higher doses also inhibited theophylline-stimulated lipolysis. The N₆-2-0′dibutyryl derivative of cyclic adenosine monophosphate (DCAMP) stimulated lipolysis. Prostaglandin E₁ did not significantly inhibit the lipid mobilizing effects of DCAMP. Changes in glycogen phosphorylase activity after treatment with theophylline, norepinephrine, DCAMP, and PGE₁ paralleled those of lipolysis. These results suggest that in man as in experimental animals lipolysis and phosphorylase activity are regulated through processes involving cyclic AMP and that PGE₁ appears to exert its antilipolytic effect in human fat cells, as in rat fat cells, by interfering at the level of adenyl cyclase with the accumulation of cyclic AMP.