dibutyryl-cyclic-gmp and benzotript

The abilities of the pancreatic cholecystokinin (CCK) receptor antagonists dibutyryl cyclic GMP, proglumide, benzotript, CBZ-tryptophan, CBZ-cysteine and CCK-27-32-amide to inhibit CCK binding to its receptor in the pancreas and brain of mice and guinea pigs was examined. In both species, the same relative potencies of the antagonists in brain and pancreas was seen except that dibutyryl cyclic GMP was considerably more potent on pancreas than on cerebral cortex CCK receptors. CCK-27-32-amide was the most potent inhibitor for both brain and pancreas but was more potent in the guinea pig than in the mouse. Proglumide, a relatively weak antagonist, was a more potent inhibitor of the guinea pig than of the mouse pancreas receptor. Thus, these data suggest that there are both tissue-specific and species-specific differences in CCK antagonist interactions with the CCK receptor.

Topics: Animals; Benzamides; Binding, Competitive; Brain; Cysteine; Dibutyryl Cyclic GMP; Guinea Pigs; In Vitro Techniques; Male; Mice; Oligopeptides; Pancreas; Proglumide; Receptors, Cell Surface; Receptors, Cholecystokinin; Structure-Activity Relationship; Tryptophan

In dispersed acini from guinea pig pancreas, proglumide (DL-4-benzamido-N, N-dipropylglutaramic acid) and benzotript (N-p-chlorobenzoyl-L-tryptophan) caused a rightward shift in the dose--response curve for cholecystokinin-stimulated amylase secretion but did not alter the maximal increase in amylase secretion caused by cholecystokinin. At relatively low concentrations, proglumide did not alter the stimulation of enzyme secretion caused by secretagogues whose effects are mediated by adenosine 3'5'-monophosphate (e.g., vasoactive intestinal peptide or secretin) and did not alter the stimulation of enzyme secretion caused by secretagogues that have a mode of action similar to that of cholecystokinin but act through different receptors (e.g., bombesin, physalaemin, eledoisin, and ionophore A23187). There was a close correlation between the ability of proglumide or benzotript to inhibit binding of 125I-labeled cholecystokinin to its receptors on pancreatic acini and the abilities of these compounds to inhibit the action of cholecystokinin on enzyme secretion and on calcium outflux. These results indicate that proglumide and benzotript are members of a different class of cholecystokinin receptor antagonists.

Topics: Amylases; Animals; Benzamides; Carbachol; Cholecystokinin; Dibutyryl Cyclic GMP; Glutamine; Guinea Pigs; Kinetics; Male; Pancreas; Proglumide; Receptors, Cell Surface; Receptors, Cholecystokinin