Relationships among canine interdigestive exocrine pancreatic and biliary flow, duodenal motor activity, plasma pancreatic polypeptide, and motilin

Abstract

To evaluate the cyclic patterns of interdigestive pancreatic and biliary flows into the duodenum and to correlate these and the plasma levels of pancreatic polypeptide and motilin with duodenal interdigestive motor activity, five dogs were surgically prepared with three indwelling duodenal catheters. Through the first catheter, located just distal to the pylorus, a nonabsorbable marker was perfused at 3 ml/min. The second catheter, opposite the main pancreatic duct orifice, was water-filled and was used to continuously record duodenal pressures and also to deliver pulses of a second nonabsorbable marker in order to measure transit time through the duodenum and sampling catheter. From the third catheter, 10 cm distal to the second, duodenal samples were continuously collected by siphonage. Twominute aliquots were analyzed for trypsin, bile acids, bicarbonate, and markers. At the beginning and end of each phase of motor activity, blood samples were analyzed for pancreatic polypeptide and motilin. Four phases of duodenal interdigestive motor activity were defined. During phase I, outputs of trypsin, bile acids, and bicarbonate were absent or minimal. During phase II, maximal outputs of trypsin and bile acids occurred. During phase III, there was a trend toward maximal bicarbonate output, but this was not significantly greater than the output during phase II. Low plasma levels of pancreatic polypeptide and motilin were present during phase I. Peak levels of pancreatic polypeptide occurred during phases II and III, and peak levels of motilin occurred during phases III and IV. In summary, pancreatic and biliary flows into the duodenum are cyclic and associated with interdigestive motor activity. Cyclic changes of plasma motilin and pancreatic polypeptide also were associated with changes in pancreatic and biliary flows into the duodenum and intestinal motor activity, but whether these events are modulated by motilin or pancreatic polypeptide is uncertain.