Exogenous CCH and gastrin stimulate pancreatic exocrine secretion via CCK-A but also via CCK-B/gastrin receptors in the calf

A predominance of the pancreatic cholecystokinin (CCK) receptor of the B/ga strin subtype (CCK-B/G) was reported in calves older than 1 month. Specific CCK-A and CCK-B/G receptor antagonists (SR 27897 and PD 135158, respective ly) were used to identify the CCK receptor subtype involved in exogenous CC K- and gastrin-induced exocrine pancreatic responses. Conscious calves (2 m onths old) with catheterized pancreas, jugular vein and duodenum were used: the pancreatic juice was continuously reinfused. CCK (30 pmol kg(-1) min(- 1), 40 min) evoked an increase in pancreatic juice flow and enzyme secretio n, while the same dose of gastrin increased enzyme secretion alone. CCK-ind uced pancreatic secretion was abolished by SR 27897 (15 nmol kg(-1) min(-1) , 55 min) and reduced by PD 135158 (0.15 nmol kg(-1) min(-1), 55 min). Gast rin-induced enzyme secretion was reduced by PD 135158 (50% to 90%) and to a lesser extent by SR 27897 (50% to 60%). These results demonstrate that CCK and gastrin in the physiological range stimulate pancreatic exocrine secre tion in calves and that these effects are partly mediated by CCK-B/G recept ors. Although CCK-A receptors are not predominantly expressed, they seem to play a major role in the response of pancreatic exocrine secretion to CCK.