CCK-INDEPENDENT INCREASES IN PANCREATIC-SECRETION INDUCED BY DIETARY-PROTEIN IN CHRONIC BPJ-DIVERTED RATS

Previously, we demonstrated that, in rats with chronic bile-pancreatic juice (BPJ) diversion, pancreatic enzyme secretion was increased afte r feeding animals a 25% casein fat-free diet. We determined whether ch olecystokinin (CCK) or the cholinergic pathway is associated with the response of pancreatic secretion after protein ingestion in the divert ed rats, using a potent CCK antagonist, MK-329 or FK-480, and a cholin ergic blocker, atropine. Secretion rates of chymotrypsin and trypsin i n the fasting state were very high 7 days after a BPJ diversion, and t he hypersecretion of the proteases was markedly reduced with an inject ion of MK-329, FK-480, or atropine and was further reduced by combined injection of FK-480 and atropine. The lowered secretion of the protea ses in CCK-antagonized rats was increased after oral feeding of a prot ein diet and after a duodenal instillation of some protein sources, es pecially hydrolysate of guanidinated casein (HGC). The CCK-independent increases by HGC instillation are completely depressed by atropine. I n rats treated with only atropine, the lowered secretion tended to be increased by a duodenal instillation of HGC. Increases in secretion af ter an administration of the protein source in CCK-antagonized rats we re not affected by bestatin, an inhibitor of brush-border peptidases. We conclude that the stimulatory effects of dietary protein on the pan creatic enzyme secretion partially do not depend on CCK in chronic BPJ -diverted rats and that the CCK-independent increase is atropine sensi tive.