The Effect of Raw Soybean Meal and Trypsin Inhibitor Diets on Pancreatic Enzyme Secretion in the Rat

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Abstract
The influence of raw soybean and crystalline trypsin inhibitor on pancreatic enzyme secretion in the small intestine of the rat was investigated. Animals that had been trained to eat their daily food requirement in two hours were used to follow the enzyme response at different intervals after eating. The results showed that immediately after ingesting a 50% raw soybean meal diet intestinal amylase and lipase activity increased. By three hours, the concentration of enzyme was three or 4 times that produced with the heated meal. The enhanced intestinal enzyme activity was reflected by a concomitant depletion of pancreatic enzymes. Intestinal trypsin activity was low immediately after eating but increased steadily and by 6 hours was three times the normal concentration. The low initial activity apparently resulted from inactivation by the inhibitor, while the later rise in activity was due to pancreatic secretory stimulation. A crude preparation of soybean antitrypsin as well as crystalline soybean inhibitor also produced the pancreatic response, so the stimulating agent in raw soybean must be the antitrypsin. Pepsin secretion was unaffected by raw soybean which suggested a specific effect of the inhibitor on the pancreas. The high level of intestinal trypsin produced would seem to argue against the concept that intestinal proteolysis in the rat is seriously impaired by the soybean trypsin inhibitor.