IMMUNOHISTOCHEMICAL DIFFERENTIATION OF GASTRIN AND CHOLECYSTOKININ INGASTROINTESTINAL-TRACT OF CHICKENS

The presence of cholecystokinin (CCK) in the gastrointestinal tract of chickens has not been well demonstrated, although immunological and c hromatographic techniques have shown the presence of intestinal gastri n-CCK-like factors. Recently, a new peptide, structurally related to m ammalian CCK, but with a gastrin-like activity, has been isolated from the digestive tract of chickens. The objective of this work has been: 1) to study the presence of gastrin-CCK-like immunoreactivity (IMR) i n the digestive tract of chickens; 2) to distinguish chicken gastrin f rom CCK; and 3) to establish their distribution using specific antibod ies. Tissue specimens from the proventriculus, gizzard, pylorus, duode num, jejunum, ileum, ceca, and rectum were studied using indirect immu nofluorescence procedures. The antibodies used were: 1) an antibody sp ecific against the C-terminal pentapeptide common to gastrin and CCK; 2) one specific against CCK-33; and 3) one specific against chicken ga strin. Their use allowed the differentiation of two cellular populatio ns which showed different affinities for the antibodies, indicating th e presence of a gastrin-like peptide in the antrum and another CCK-lik e peptide in the small intestine, with the highest concentration in th e proximal ileum. Immunoreactivity was not found in any other studied area. Two different peptides of the gastrin-CCK family are present in the chicken's gastrointestinal tract. However their differentiation an d identification are more difficult than in mammals due to the greater structural similarities of these peptides in birds.