Somatostatin enhances the inhibitory effect of oxyntomodulin and its C-terminal octapeptide on acid secretion

Somatostatin (SOM) and oxyntomodulin (OXM) are two natural peptides present in the gut which display inhibitory effects on gastric acid secretion in rat. Possible interactions between the effects of these two molecules were tested in the anesthetized rat, using as the stimulant either pentagastrin or histamine at doses that induced 30% of the maximal responses. SOM was tested at sub-threshold doses and OXM at doses inducing an inhibition of less than 50%. SOM induced a highly significant potentiation of the action of OXM both on pentagastrin- and histamine-induced secretion. Similarly, SOM enhanced the inhibitory effects of the C-terminal octapeptide of OXM. Whatever the mechanism involved, this potentiating effect of SOM might be of importance in the in vivo biological effect of OXM.