Modulation of cytochrome P-450 induction by long-term food restriction in male rats.

The influence of food restriction (FR) on the induction of liver microsomal cytochrome P-450 (P-450) was examined in rats, FR by 40% for 6 weeks caused increase in the levels of P-450, cytochrome b5 (b5), NADPH P-450 reductase, NADH b5 reductase, P-450 dependent testosterone 6 beta-, 16 alpha- and 16 beta-hydroxylases (P < 0.05). Treatment of 3-methylcholanthrene (MC) to food restricted rats (FR rats) induced more P-450, but phenobarbital (PB) induced it less. MC-inducible P-450 from FR rats did not increase its specific ethoxycoumarin O-deethylase activity but it increased testosterone 2 alpha-hydroxylase activity, and the maximum absorption of its CO complex was shifted from 448 nm to 450 nm. PB-inducible P-450 showed less increase in the activities of its specific benzphetamine N-demethylase and it rather significantly decreased testosterone 16 alpha-hydroxylase activity (P < 0.05). These results indicate that the drugs did not induce their unique types of P-450 in FR rats. Such alterations in P-450 induction in FR rats seem to be closely related to the level of P-450 and its related components enhanced by FR, and it could result in modulation of mixed function oxidase system.