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.