Effect of protein infused into sheep duodenum on activities of pancreatic proteases in intestinal digesta and on the absorption site of amino acids.

The effect of increasing the flow of protein amino acids to the small intestine on the activities of pancreatic proteases and on the absorption site of amino acids was examined in sheep equipped with intestinal cannulas at 0.05, 11 and 25 m from the pylorus. A single concentrated diet providing 85.1 g of protein amino acids/day was fed throughout the experiment. During period 1 this was the only source of protein. During period 2, a suspension of casein was infused into the duodenum through the 0.05-m cannula at a rate of 100 g/day, which supplied to the small intestine a total of 177 g amino acids/day. In period 1, 56.7 g of amino acids was absorbed per day along the entire small intestine, and 85% of it was absorbed in the anterior 11 m. Of the 143 g of amino acids absorbed per day during period 2, 63% was absorbed in the anterior 11 m. Ninety-four percent of the infused casein was absorbed. Increasing the flow of amino acids to the small intestine of sheep from 85 to 177 g/day resulted in an overall elevation in the activities of chymotrypsin, carboxypeptidase A and trypsin at the 11-m site but not the 25-m site. The greatest increase was obtained with chymotrypsin: 119 and 114% for the specific and total activities, respectively, and the least with the trypsin: 38 and 36% for the specific and total activities, respectively.