Chronic and acute studies indicating absence of exocrine pancreatic feedback inhibition in dogs.

Chronic administration of raw soybean flour containing active trypsin inhibitor to dogs reduced the pancreatic output of trypsin and chymotrypsin in response to cholecystokinin. Dogs stimulated by a meat meal showed no consistent alteration in the output of trypsin and chymotrypsin when given additional duodenal infusions of trypsin and chymotrypsin, or canine pancreatic juice, or ovalbumin trypsin inhibitor. Two dogs, whose pancreas was stimulated by intraduodenal infusion of amino acids, showed no consistent change when trypsin, or trypsin together with trypsin inhibitors, or trypsin together with canine pancreatic juice was infused concurrently into the duodenum. These results indicate that feedback control of pancreatic enzyme secretion, of the type proposed on the basis of studies similar to the present in rats, does not exist in dogs.