Exocrine pancreatic response to isoproterenol in the rabbit under secretin and CCK stimulation

The effect of isoproterenol (0.3 micrograms/Kg/min) on exocrine pancreatic secretion stimulated by secretin (1. C.U./Kg/h) and the octapeptide of cholecystokinin (OP-CCK 0.15 Ivy dog units/Kg/h) was studied in anaesthetized rabbits. Pancreatic blood flow remained unaffected by the action of isoproterenol; however, the administration of the beta-adrenergic agonist over an infusion of secretion an OP-CCK led to an increase in pancreatic juice flow (approximately 146% for secretin and 125% for OP-CCK) and HCO3-output (approximately 194% for secretin and 150% for OP-CCK), a potentiation being observed between the effects of secretin and isoproterenol. This kind of response, independent of vascular changes, is due to a direct action of isoproterenol on the ductular cells. Isoproterenol interferes with the action of secretin and OP-CCK in that it partially inhibits the stimulatory action of OP-CCK on the enzymatic secretion of the acinar cells in the rabbit pancreas and at the same time protein secretion decreases in the presence of secretin.