LONG-TERM CONSUMPTION OF AN AMINO-ACID DIET REDUCES THE PANCREATIC-ENZYME SECRETION RESPONSE TO A TRYPSIN-INHIBITOR IN RATS

We investigated pancreatic enzyme secretion in response to soybean try psin inhibitor (SBTI) in rats fed amino acids as a nitrogen source, fr om the fetal stage to adulthood. Pregnant rats were divided into two g roups 4 d before parturition. During gestation and nursing, one group was fed a 15% protein diet (protein-fed rats) and the other (amino aci d-fed rats) a 15% amino acid mixture diet that simulated the compositi on of the protein diet. Each male offspring was weaned at 4 wk after p arturition and fed the same diet as fed to its dam for an additional 6 wk. Pancreatic amylase secretion in response to an intraduodenal infu sion of SBTI (10 mg/rat) was observed in the protein-fed rats but not in the amino acid-fed rats. Amylase secretion in response to an intrav enous injection of cholecystokinin (CCK) (10 ng/kg rat) was observed i n both groups, and the magnitude of the response was significantly hig her in the amino acid-fed rats than in the protein-fed rats. An increa se in the level of plasma CCK in response to SBTI was observed in the protein-fed rats but not in the amino acid-fed rats. These results sug gest that the long-term amino acid diet, because of its ability to inh ibit the SBTI-stimulated CCK-releasing process in the small intestine of rats, reduced the pancreatic enzyme secretion response to a trypsin inhibitor. Six rats fed the amino acid mixture until 1 wk after weani ng were fed the protein diet for the next 5 wk. These rats showed no p ancreatic amylase secretion in response to SBTI, suggesting that dieta ry components around the weaning stage may affect the development of t he ability of small intestinal cells to recognize a trypsin inhibitor.