Effect of individual l-amino acids on gastric acid secretion and serum gastrin and pancreatic polypeptide release in humans.

Individual l-amino acids were instilled intragastrically to determine possible differences in stimulation of gastric acid secretion and gastrin and pancreatic polypeptide release. Phenylalanine and tryptophan were significantly more potent stimulants of gastric acid secretion and of pancreatic polypeptide and gastrin release than any of the other amino acids tested. Smaller, but significant, responses were obtained with threonine for pancreatic polypeptide and with serine for acid secretion. We conclude that a major part of the acid-stimulating action of mixed amino acid solution can be explained by the aromatic amino acids, phenylalanine and tryptophan, which are also the most potent stimulants of gastrin and pancreatic polypeptide release. These studies suggest that the specific composition of amino acid mixtures determines the net effects of such mixtures on gastric secretion, and on release of both the antral hormone gastrin and the pancreatic hormone, pancreatic polypeptide.