Effects of the Prostaglandins on Hormone-induced Mobilization of Free Fatty Acids *

Abstract

Prostagiandin E1 (PGE1) at 2.8 x 10-7 [image] concentration effectively counteracted the fat-mobilizing activities of epinephrine, norepinephrine, adrenocorticotropic hormone, glucagon, and thyroid-stimulating hormone on the rat epididymal fat pad in vitro, measured in terms of glycerol release into the medium. In the absence of added hormones, the rate of glycerol release from fat pads was slightly decreased by PGE1. PGE1 interfered with the epinephrine-induced activation of a hormone-sensitive lipase in adipose tissue. There was also a small but significant interference with epinephrine-induced activation of phosphorylase. The relative potentcies of a series of closely related compounds in the prostaglandin family as inhibitors of epinephrine-induced fat mobilization in vitro were determined. The high potency of PGE1 as a vasodepressor agent was confirmed. When injected intravenously into dogs along with approximately equimolar amounts of epinephrine or norepinephrine, PGE1 counteracted the pressor activity of the catecholamines as well as the rise in plasma free fatty acids normally produced. The hyperglycemic response to epinephrine did not appear to be altered.