Rapid changes in pancreatic DNA, RNA and protein in the rat during pancreatic enlargement and involution.

Pancreatic weight, nucleic acid content and protein content were measured on the involuting rat pancreas after its initial enlargement from a raw soy bean flour (RSF) diet. Rats were fed an RSF diet for four weeks and then changed to an inhibitor-free diet of either heated soy bean flour (HSF) or rat cubes for 1, 2, 7 or 14 days. Control rats were fed cubes continuously from weaning or cubes followed by HSF for two weeks. There was no significant difference in the body weights of rats in any of the test or control groups. After four weeks on RSF the wet weight of the pancreas was double that of the control animals and the protein content and nucleic acid content were also significantly greater. After RSF-fed animals were changed to cube or HSF diets, pancreatic parameters rapidly reverted to normal. The most striking change was in pancreatic DNA which returned to control values within 2 days of changing to cubes or HSF. Pancreatic weight, RNA and protein reverted to control values within 7 days of the change of diet. The rapid increase and decrease in the size of the rat pancreas after diet alterations suggest that pancreatic growth may be more labile than previously thought. If rapid changes in pancreatic cell number occur in rats fed alternating cube and RSF diets, then these animals may be more susceptible to pancreatic carcinogens.