Effect of cionin on histamine and acid secretion by the perfused rat stomach.

The protochordean octapeptide cionin is structurally a hybrid of mammalian cholecystokinin (CCK) and gastrin. An earlier study has shown that cionin in mammals stimulates gallbladder contraction and gastric somatostatin release, similarly to CCK-8. In the present study we examined the effect of cionin on histamine release and acid secretion of the stomach, both effects being mediated by CCK-B/gastrin receptors. Cionin induced a concentration-dependent increase in histamine release and acid secretion in the isolated, vascularly perfused rat stomach, detectable at a concentration of 4 pM and reaching a maximum at a concentration of 512 pM. The CCK-B/gastrin receptor antagonist L 365,260 abolished the stimulating effect of cionin on both histamine release and acid secretion, whereas the CCK-A receptor antagonist L 364,718 only had a faint effect. Cionin is a potent and efficient stimulator of gastric histamine release and acid secretion interacting via a CCK-B receptor.