Octreotide (SMS 201-995) is a long-acting somatostatin analogue that inhibits exocrine pancreatic secretion and that has been proposed for treatment of various pancreatic disorders. To gain more information about the mechanism by which octreotide inhibits pancreatic enzyme secretion, we studied the effect of this compound on plasma amino acid uptake by the pancreas in six healthy volunteers aged 22-29 years. Pancreatic amino acid uptake was assessed by measuring plasma amino acid concentration before and during pancreatic enzyme synthesis stimulation with cerulein (50 ng/kg/h). The infusion of cerulein caused a significant decrease (p less than 0.001) in plasma amino acid concentration. The subcutaneous injection of octreotide at dosages of 12.5, 25, and 50 micrograms prevented this decrease in a dose-dependent manner. The decrease in amino acid concentration reached a maximum of 19.4 +/- 2.4% during cerulein infusion and a maximum of 10.7 +/- 2.5, 6.8 +/- 1.2, and 2.9 +/- 1.2% (means +/- SD) when cerulein was preceded by injection of octreotide at 12.5, 25, and 50 mg, respectively. These results indicate that octreotide is able to inhibit the plasma amino acid uptake by pancreatic acinar cells and, consequently, synthesis of pancreatic enzymes. Clinically, this effect could be useful in treatment of pathologic conditions of the pancreas in which it is desirable to suppress acinar cell activity and avoid accumulation of enzymes in acinar cells.