The effect of a low protein diet on the response of rat colonic and hepatic ornithine decarboxylase activity to sodium deoxycholate and thioacetamide treatment.

Adult male Sprague-Dawley rats fed ad libitum AIN-76A diet with 5% casein for 10 days had the same basal level of colonic ornithine decarboxylase (ODC) as rats fed 20% casein, but showed a higher level following induction of the colonic enzyme by sodium deoxycholate. Total colonic ODC activity was more responsive than holo-ODC activity to the regimen of induction, which suggested to us that functional (i.e., holoenzyme) levels of the decarboxylase may not be as sensitive to dietary modulation as total enzyme levels. Contrary to the results observed for the colon, the basal level of hepatic ODC was decreased in rats fed 5% casein, and the level following induction of the hepatic enzyme by thioacetamide was also diminished compared with induced enzyme levels in animals fed 20% casein. Additionally, there was no difference in the degree of response between holoenzyme and total hepatic enzyme to dietary treatment and a regimen of enzyme induction.

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.