Influence of several plant and animal proteins on rat pancreas

Twelve different plant and animal proteins were fed to rats for 4 weeks. Trypsin inhibitor (TI) content of the diet was significantly correlated with (although not directly related in all cases to) pancreas weights and with the pancreatic biochemical parameters that indicate hypertrophy. In vitro, but not in vivo, digestibility was correlated with the TI content of the diet. Quantity of DNA per gram pancreas was not found to be related to TI content. A second experiment compared graded levels of TI from raw or heated soy flour and soy protein isolate (SPI). The SPI diet produced higher relative pancreas weights per TIU than did the flour diets. Two commercial SPI's were fed as is or autoclaved in a third experiment. Autoclaving to very low TI values made no improvement in weight gain or pancreatic parameters measured, indicating that there may be a threshold level of TI below which rat pancreata do not respond, and that other factors in SPI are responsible for the slight pancreatic enlargement seen with SPI compared to casein.