Pancreatic protease secretion profiles after spontaneous feeding of casein or soybean protein diet in unrestrained conscious rats

Abstract

Under unrestrained physiologic conditions, the exocrine pancreatic secretion of digestive enzymes were observed with chronic bile-pancreatic duct cannulated rats. Bile-pancreatic juice (BPJ) was intermittently collected after spontaneous feeding of an 8% casein or an 8% soybean protein isolate (SPI) diet under recirculation of BPJ to the duodenum. The operative damage of cannula implantation was recovered for 5 days on a 25% casein diet, which was examined by food consumption and the basal secretion (pancreatic secretion during fasting) of total protein and trypsin. After feeding of both the test diets, the secretions of total protein, trypsin, chymotrypsin, and carboxypeptidase A were increased rapidly and about two-fold from the basal secretion. There were peak values at 15 min in the SPI group and at 30 min in the casein group. In the casein-fed rats, the protein and protease secretions maintained high levels for the initial 150 min, but in the SPI fed rats those secretions were decreased from 15 min after feeding. The protein and protease secretions tended to be higher in the casein group than in the SPI group after 30 min, and effect of ‘diet’ was significant in analysis of variance. The secretion profiles of protein and three proteases were similar, and specific activities of three proteases were not increased significantly in both the groups. We conclude that these low-protein diets are potent stimulators of the exocrine pancreatic secretion after spontaneous feeding in unrestrained rats.