Effects of acute and chronic protein deprivation on ornithine decarboxylase levels in rat liver and colon.

The effects of protein intake on the levels of total and holo-ornithine decarboxylase (ODC) in colon and liver have been examined in male Sprague-Dawley rats fed varying amounts of casein in a defined purified diet. Pair-feeding was used to eliminate effects of food intake per se. In the colon, both total and holo-ODC activity increased in animals fed a low-protein diet (1% casein). In the liver, on the other hand, both total and holo-ODC activity decreased with protein deprivation. The observed changes in both colon and liver appeared to be maximal within several days after institution of the dietary regimen. Refeeding with a high-protein diet (20% casein) led to a dramatic rise in ODC activity in the liver in animals previously fed a low-protein diet. These results may be important in sorting out the effects of diet on the tumorigenic process.