Nutritional Effects Induced in Rats by Feeding Natural and Synthetic Trypsin Inhibitors

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Abstract
In order to evaluate and compare the nutritional effects induced in rats by feeding navy bean trypsin inhibitor (NBTI), a natural inhibitor, with p-aminobenzamidine (p-ABA), rats were fed the following diets: 1) basal diet consisting of heated navy bean meal (control), 2) basal plus navy bean trypsin inhibitor (NBTI), and 3) basal plus p-aminobenzamidine (p-ABA), a synthetic trypsin inhibitor. Diets 2 and 3 caused growth inhibition, reduced protein efficiency ratio (PER), and pancreatic enlargement as compared to control. The supplementation of diets 2 and 3 with cystine increased growth and PER to a limited extent, whereas they were markedly stimulated by antibiotics. Supplementation with cystine or antibiotics or both had no effect either on the size or enzyme secretion of pancreas. In general, enzyme activities in pancreas and intestine were higher on diet 3 followed by diets 2 and 1. The fecal excretion of representative amino acids under study was similar in rats fed diets 1, 2, and 3. This was also true when antibiotics were added to the above diets. It appears that the nutritional effects induced in rats by feeding a natural or synthetic trypsin inhibitor are similar. The possible action of antibiotics and the failure of cystine supplement in improving the PER of diets containing the inhibitors are discussed.