Movement of free fatty acids into and out of the blood stream in normal rabbits and in rabbits injected subcutaneously with the pituitary adipokinetic substances, Fraction H and adrenocorticotropin

Abstract

Uptake and release of plasma free fatty acids by the tissues of the rabbit were investigated by measuring the arteriovenous difference in plasma FFA concentration across the perirenal fat depot, intestines and mesentery, leg, kidney, and liver. In animals given subcutaneous injection of glucose, the arteriovenous difference was negative (net release) across the intestines and mesentery, positive across the perirenal fat depot and kidney, and positive or negative across the leg and liver. After subcutaneous injection of a pituitary adipokinetic substance, either Fraction H or adrenocorticotropin (ACTH), the arteriovenous difference was negative across the perirenal fat depot, the intestines and mesentery, and the leg, while large positive differences (net uptake) were found across the kidney and liver. Stainable lipid was present in the hepatic cord cells and the cells of the renal convoluted tubules 1 hr after injection. The exchange of glucose between tissues and blood stream was not altered during adipokinesis.It is concluded that in glucose-treated rabbits, large fat depots take up FFA from the blood stream; in contrast, following the subcutaneous injection of Fraction H and ACTH, FFA are mobilized from adipose tissue into the blood stream. During the mobilization of FFA, the kidney and liver take up FFA, which probably are synthesized into triglycerides in the hepatic cord cells and cells of the renal convoluted tubules.