Radioreceptor and biological characterization of cholecystokinin and gastrin in the chicken.

Radioimmunoassay, radioreceptor assays, and bioassays were used to demonstrate that chicken brain and antrum extracts contain cholecystokinin (CCK)-like and gastrinlike peptides, respectively. C-terminal-specific radioimmunoassay of partially purified chicken CCK and gastrin gave dilution curves parallel to those of the mammalian peptides. Mouse cerebral cortical and rat pancreatic membrane radioreceptor assays were used to differentiate CCK- from gastrinlike peptides on the basis of the different CCK versus gastrin specificities of the two receptors. Confirmation of the biological activity of chicken brain CCK was obtained by stimulation of amylase secretion from rat pancreatic lobules in vitro. The specificity of this response was demonstrated by the inhibition of chicken CCK-stimulated amylase secretion by the specific CCK receptor antagonist dibutyryl cGMP. Chicken antral gastrin stimulated gastric acid secretion from the rat stomach in vivo. In contrast to previous hypotheses, it is proposed that chickens have significant amounts of an antral gastrinlike peptide and that therefore it is possible that gastrin is involved in the physiological regulation of gastric acid secretion in chickens.