Neither glycine-extended gastrin nor the 1-13 fragment of gastrin 17 influences gastric acid secretion in humans.

The effect on gastric acid secretion of two gastrin 17-related peptides without the carboxyamide, i.e., the glycine-extended 5-17 fragment and the 1-13 fragment of human gastrin 17, was examined in normal subjects. Acid secretion was stimulated by an intravenous infusion of 21 pmol/kg.h of gastrin 17 or by intragastric instillation of peptone; gastric acid output during simultaneous infusion of 325 pmol/kg.h of the glycine-extended 5-17 fragment or 319 pmol/kg.h of the 1-13 fragment was then compared with acid output during infusion of saline. Neither the glycine-extended 5-17 fragment nor the 1-13 fragment of gastrin 17 influenced gastric acid secretion. By gel and ion-exchange chromatography of serum drawn during infusion, the infused peptide was recovered at the position of the intact synthetic peptide. The disappearance curve of circulating glycine-extended gastrin could be described by two components with half-lives of 3.6 and 48 min. As the glycine-extended fragment was stable in serum or plasma in vitro for 1 h at 37 degrees C, the rapid elimination observed in vivo cannot be ascribed to circulating plasma enzymes.