Relationship between amino acid transport and protein synthesis in rat isolated pancreatic acini under stimulation with cholecystokinin.

The effects of cholecystokinin octapeptide (CCK8) on amino acid transport and protein synthesis in the pancreatic acini were determined. The question of whether those effects differed between amino acid transport systems A and L was also investigated. The influx of alpha-[3H]aminoisobutyric acid (AIB, system A) and [14C]cycloleucine (system L) into isolated rat pancreatic acini and the incorporation of [14C]alanine (system A) and [3H]leucine (system L) into trichloroacetic acid (TCA)-precipitable protein in pancreatic acini were studied in the presence of various concentrations of CCK8. CCK inhibited the amino acid transport across the basolateral membrane of pancreatic acini. This effect was mediated by Ca2+, and was more responsive to amino acid transport system L than to A. CCK also inhibited protein synthesis in pancreatic acini in a dose-dependent manner. The inhibition of protein synthesis by CCK was thought to be mainly due to the inhibition of amino acid transport by CCK. Therefore, the predominant utilization of extracellular amino acids in protein synthesis was suggested.