Regulation of the Transport and Metabolism of Amino Acids in Isolated Fat Cells

摘要: Abstract We investigated the effects of insulin on amino acid transport, protein synthesis, and breakdown in fat cells isolated from rat epididymal adipose tissue. Insulin stimulated accumulation 14C-labeled proteins incubated with l-leucine, l-alanine, glycine, l-serine. With l-leucine-1-14C as a model acid, we observed that did not require addition glucose or other carbohydrate to incubation medium, were produced by concentrations comparable those required accelerate transport. The was inhibited adrenocorticotropic hormone (ACTH) theophylline at known increase adenosine 3',5'-monophosphate (cyclic AMP) cells. inhibitory ACTH reversed insulin, while plus only partially reversed. High N6, 21-O-dibutyryl cyclic AMP duplicated theophylline. had slight inhibition dibutyryl AMP. Amino transport assessed measuring intracellular α-aminoisobutyric (AIB), 1-aminocyclopentane-1-carboxylic certain natural acids. labeled acids achieved extracellular concentration ratios which similar measured fresh AIB Na+-dependent temperature-sensitive 20:1 molar excess but glucose-independent affected ACTH, theophylline, change initial rate uptake, efflux, equilibrium cycloleucine. When synthesis blocked 10-4 m puromycin, effect breakdown. This "antiproteolytic" could fully account for stimulatory proteins. concluded predominant exerted some unidentified step rather than steps Furthermore, postulated might act negative effector action synthesis.