PANCREATIC DIGESTIVE HYDROLASE ACTIVITIES IN GROWING RATS FED ALTERNATELY ON RAW AND HEATED SOYBEAN FLOUR

The time-course effects of two diets containing raw (RSF) or heated (H SF) soya-bean flour on the digestive enzyme levels in the pancreas and in pancreatic juice were investigated in growing rats fed, alternatel y, on RSF or HSP diets for two 4-week periods. These values were compa red with those obtained in a control group fed on a casein diet. RSF a nd HSF diets lowered N balance (84.8 (SE 0.9), 82.6 (SE 0.8) and 79.9 (SE 0.8) % with control, HSF and RSF diets respectively, at the third week). However, they increased protease activities compared with the c ontrol diet (3-fold for trypsin (EC 3.4.21.4) and chymotrypsin (EC 3.4 .21.1) activities in pancreas contents and outputs with the RSF diet; 2-fold for trypsin in pancreas contents and outputs and by 60% for chy motrypsin contents with the HSF diet). The poorer nutritional N utiliz ation might be attributable to soya-bean flour heat-stable (lectins) a nd heat-labile components (trypsin inhibitors). The decrease in lipid apparent digestibilities in RSF and HSF diets (97.0 (SE 0.8), 98.1 (SE 0.9) and 90.4 (SE 0.7) % with control, RSF and HSF diets at the seven th week) were correlated with a diminution in apparent lipase (EC 3.1. 1.3; measured without addition of exogenous colipase), potential lipas e (measured with addition of saturated amounts of exogenous colipase) and colipase activities. Compared with control values, gains in potent ial and apparent lipase outputs were diminished by nearly 40 % and gai n in colipase outputs by 60% with RSF and HSF diets. These results sho w clearly that heated or raw soya-bean flours have a significant inhib itory effect on lipase digestive enzyme activities in the pancreas and in its secretion, which might explain impaired lipid digestibility.