Studies on the Metabolism of Adipose Tissue

Abstract

In previous studies in this series (l-3) it has been shown that an action of insulin on the metabolism of adipose tissue may be readily demonstrated by measurement of the net gas exchange in a bicarbonate medium. In this paper, we present data on glucose consumption, lactate production, and net gas exchange as measured concomitantly on the rat epididymal fat pad in the presence and absence of insulin. In addition the effect of adrenaline alone and in combination with insulin on these same metabolic processes in a bicarbonate medium has been measured. A study of the action of adrenaline on adipose tissue is prompted in part by the fact that this hormone has been shown to stimulate triglyceride breakdown in this tissue in vitro with the release of nonesterified fatty acids into the incubation medium (4-6). In addition it is known that adrenaline influences lipid metabolism in other tissues, inhibiting fatty acid synthesis in liver slices (7, 8) and increasing fatty acid oxidation in liver slices (9) and liver homogenates (10, 11). Glucose metabolism of adipose tissue is also influenced by adrenaline as indicated by stimulation of glycogen breakdown in viva (12) and by phosphorylase activation in vitro (13).