Glycine-extended gastrin potentiates gastrin-stimulated gastric acid secretion in rats

The purpose of this study was to examine whether an intermediate form of amidated gastrin, glycine-extended gastrin (Gly-G), can stimulate gastric acid secretion in conscious rats prepared with gastric fistulas. Intravenous administration of Gly-G (20 nmol · kg^-1 · h^-1) alone for 2 h did not stimulate gastric acid secretion; however, administration of Gly-G (20 nmol · kg^-1 · h^-1) in combination with a bolus administration of gastrin (9.5 nmol/kg) potentiated acid secretion significantly. Gastric acid secretion in response to gastrin alone and gastrin plus Gly-G (2 nmol · kg^{- 1} · h^-1) was 109.1 ± 21.6 and 170.1 ± 27.7 μeq · kg^-1 · h^-1, respectively (P < 0.05). Gastric acid secretion in response to gastrin alone and gastrin plus Gly-G (20 nmol · kg^-1 · h^-1) was 84.8 ± 17.5 and 164.1 ± 29.3 μeq · kg^-1 · h^-1, respectively (P < 0.05). Intravenous administration of Gly-G (20 nmol · kg^-1 · h^-1) failed to increase histamine (1 mg/kg)-stimulated acid output. These results demonstrate that Gly-G can selectively potentiate the stimulatory effect of gastrin on acid secretion in rats and that the unprocessed form of gastrin, Gly-G, can exert a biological effect in the stomach.