Lipolytic action of epinephrine in adipose tissue homogenates

Abstract

Incubation of intact adipose tissue with ACTH, certain preparations of growth hormone, and epinephrine induces an increase in lipolytic activity in homogenates prepared from this tissue. Epinephrine also causes an increase in lipolytic activity when added directly to adipose tissue homogenates. The increase is inhibited by 4 x 10^–4 m iodoacetate. Mitochondrial and "supernatant" fractions (including microsomes) and the lipid layer all possess lipase activity, but only the lipase found in the supernatant fraction can be activated by epinephrine. Protamine activates this lipase; addition of epinephrine has no additive effect. Heparin inhibits the stimulation of lipase activity by epinephrine, but has no action on the lipolysis occurring in the absence of epinephrine. It is concluded that the epinephrine-stimulated lipase is distinct from lipoprotein lipase and the lipase present in unstimulated tissue.