[Effect of a short-term protein-free diet on endogenous nitrogen secretion: exocrine pancreas secretion in the pig]

A protein-free diet is often used in animal experimentation to estimate the amount of total endogenous nitrogen secreted by the organism. To test the validity of this technique, we carried out a study on pigs describing the short-term (8-day) effect of a protein-free diet on exocrine pancreas nitrogen secretion; this nitrogen was considered as representative of total endogenous nitrogen. After 11 pigs had been adapted to a balanced diet (14% protein), they were chronically fistulated in the pancreatic duct and duodenum. Pancreatic secretion and its various parameters (volume, total protein and chymotrypsin, trypsin, amylase and lipase activities) were measured over a first experimental period of 4 days, during which the pigs continued to receive the balanced diet, and over a second experimental period of 8 days during which they were given a protein-free diet. The results show that the amount of pancreatic protein did not change during the period the protein-free diet was given. After 2 days, chymotrypsin specific activity dropped, while amylase and lipase specific activities decreased little and slowly after 6 days. However, for short-term experiments, the protein-free diet proved to be an adequate technique for determining the production of total endogenous nitrogen in the digestion tract.