Hepatobiliary and pancreatic clearance of circulating pancreatic amylase

The hepatobiliary and pancreatic uptake of pancreatic amylase was studied in the conscious rabbit. Four hours after intra-arterial injection of 125I-labeled porcine or rabbit pancreatic amylase, about 7% of the administered radioactive dose appeared in liver and bile, but less than 0.2% appeared in the pancreas and pancreatic juice. No amylolytic activity was detectable in bile, but a significant fraction of the acid-precipitable radioactive counts in bile comigrated with the injected amylase on gel autoradiography. Enzymatic activity appeared in bile after continuous intraarterial infusion of pancreatic amylase with excellent correlation between biliary and plasma amylase activities (r greater than or equal to 0.94). Only a small percentage (0.002%) of amylase delivered to liver, however, was excreted into bile. After intraduodenal instillation of radiolabeled pancreatic amylase or ribonuclease A, virtually none of the radioactivity appeared in the pancreas, and none in bile was acid precipitable. We conclude that a small but definite amount of the circulating pancreatic amylase is excreted intact into bile in the conscious rabbit. There is, however, no significant enterohepatic or enteropancreatic circulation of pancreatic enzymes.