Oxyntomodulin (glucagon-37) and its C-terminal octapeptide inhibit gastric acid secretion.

Oxyntomodulin (OXM) is a peptide isolated from porcine intestine which consists of the whole glucagon sequence with a basic octapeptide (KA8) at its C-terminal end. In this study, the effect of OXM and KA8 on pentagastrin-stimulated gastric acid secretion has been studied in conscious rats and cats. In rats, OXM (25-450 pmol . kg-1) as well as KA8 (7.5-60 nmol . kg-1) inhibited pentagastrin-stimulated gastric acid output in a dose-dependent manner; KA8 was about 100-times less potent than OXM. In cats, KA8 (90 nmol . kg-1) was also an inhibitor of acid secretion. We conclude that OXM, or a closely related peptide, could be a physiological modulator of gastric acid secretion, and that the C-terminal octapeptide of OXM is implicated in this effect.