A PROTEIN LESS SENSITIVE TO TRYPSIN, GUANIDINATED CASEIN, IS A POTENTSTIMULATOR OF EXOCRINE PANCREAS IN RATS

Previously, we have shown that, In rats that have had bile-pancreatic juice (BPJ) diverted from the proximal small intestine for 7 days, the exocrine pancreatic secretion was enhanced after they were fed a case in, fat-free diet, This demonstrates that the pancreatic secretion is stimulated by dietary protein with a pancreatic protease-independent p athway, To examine the chemical structure of casein responsible for th e enhancement of pancreatic secretion, we prepared chemically modified casein in which lysine residues were guanidinated. Secretion of prote in, amylase, and chymotrypsin in the chronic BPJ-diverted rat was incr eased much more after the rats were fed a diet containing guanidinated casein (250 g/kg diet) than after they were fed a diet containing int act casein (250 g/kg diet), In normal rats whose diverted BPJ was retu rned to the duodenum, the increases in the pancreatic secretion after consuming the guanidinated casein diet were comparable to those after consuming the intact casein diet, in vitro digestibility of guanidinat ed casein by trypsin and chymotrypsin was much lower than that of inta ct casein, Also, guanidinated casein inhibited tryptic hydrolysis of b enzoyl-L-arginine p-nitroanilide to a lesser extent than did intact ca sein as determined by an in vitro assay, These results demonstrate tha t guanidinated casein is less sensitive to trypsin than is intact case in and that the structure that is sensitive to trypsin is not involved in the stimulation of pancreatic secretion In diverted rats, The resu lts evidence that masking luminal trypsin activity does not predominan tly contribute to the enhancement of pancreatic secretion in 7-day BPJ -diverted rats, Also, in normal rats, the luminal protease-independent mechanism may play a role partly in increasing the pancreatic secreti on by dietary protein.