The adaptation of the exocrine enzymes of rat pancreas to the composition of the diet

Abstract

It was shown previously that the specific activity of amylase is higher in the pancreas of rats ingesting a starch-rich diet (rats and diet G) than in rats ingesting a protein-rich diet (rats and diet P). On the contrary, the specific activity of chymotrypsinogen was found higher in the pancreas of rats P. The investigation has now been extended to the pancreatic juices obtained from rats of both groups, to the kinetics of the adaptation process and to the effects induced in rats P by the ingestion of a glucose-rich diet instead of a starch-rich diet. 1. 1. Usually, pancreatic fistulae on rats give a flow of juice during more than 50 h. But the specific activities of the enzymes vary strongly when the collection lasts more than 20–25 h. 2. 2. Results obtained with juice samples collected during 20–25 h are similar to those previously obtained with pancrease homogenates. The specific activity of amylase is 2–3 times higher in homogenates and juices of rats G. Chymotrypsinogen is 2–3 times higher in homogenates and juices of rats P. Trypsinogen and other proteolytic precursors such as procarboxypeptidase B are also higher in rats P. Thus, there exists a real adaptation of amylase and proteolytic enzymes to the main component of the diet. 3. 3. When rats fed on a certain diet are suddenly fed on the other, the adaptation process starts without delay and lasts about 5–7 days. The new values reached by the specific activities at the end of the adaptation period are stable and reproducible. 4. 4. Another expression of the adaptation process is to determine the absolute amounts of the various enzymes flowing out in a given time from the pancreatic fistulae. It can be shown in this way that, within a given number of hours, a pancreas produces about the same amount of total proteins as a pancreas P, but 2–3 times more amylase and 2–3 times less chymotrypsinogen. 5. 5. Finally, 75% dextrose in the diet induces the same effect in rats P as 75% starch (diet G). This fact suggests that exocrine pancreas receives its information from the products formed during the digestion process, rather than from the ingested products.