α-Aminoisobutyric acid uptake in isolated mouse fat cells

Abstract

1. 1. The uptake of the amino acid analogue, α-aminoisobutyric acid into mouse isolated fat cells has been studied. 2. 2. α-Aminoisobutyric acid was found to be transported into and accumulated within the cells by a process that was both temperature and energy-dependent. 3. 3. α-Aminoisobutyric acid entry appears to be a complex phenomenon that may comprise at least two components, a saturable one, and one similar to passive diffusion. In addition, α-aminoisobutyric acid uptake was shown to be both sodium and potassium-dependent. 4. 4. Adrenaline and ACTH markedly inhibited α-aminoisobutyric acid uptake. When added together with these lipolytic hormones, insulin restored α-aminoisobutyric acid uptake towards normal. Furthermore, under certain conditions, insulin alone stimulated α-aminoisobutyric acid uptake. 5. 5. It is suggested that the intracellular concentration of free fatty acids, possibly that of ATP, may explain the action of these different hormones upon the uptake of α-aminoisobutyric acid by the fat cells, although an additional direct effect upon the transport mechaism per se cannot be excluded.