The Effect of Raw Soybean Meal and Trypsin Inhibitor Diets on the Intestinal and Pancreatic Nitrogen in the Rat

Abstract

Rats fed raw soybean diets had a higher concentration of net unabsorbed nitrogen in the intestine than did rats fed the heated protein meal. The increased nitrogen in the intestine was accompanied by a correspondingly greater depletion of pancreas nitrogen. Soybean trypsin inhibitor at 0.5% of a heated soybean diet (a level capable of evoking a pancreatic enzyme response) also increased the intestinal nitrogen. The elevated level of nitrogen could not be accounted for by the undigested inhibitor or by a failure of intestinal proteolysis. The nitrogen concentration remained high in the small intestine and cecum, but was reduced in the colon. Amylase, trypsin and lipase activity remained increased throughout the intestinal tract of animals fed raw soybean, whereas rats fed the heated meal showed almost complete destruction of the enzymes in the cecum and colon. As a result, it was suggested that the high intestinal nitrogen originated from the stimulated pancreatic secretions. A possible relation of these observations to the apparent poor utilization of unheated soybean protein was mentioned.