Effect of hyperoxia on rat pulmonary and hepatic cytochrome P450 monooxygenases

Exposure of adult male rats to hyperoxia (O-2 > 95%) resulted in a tendency for all of the components of the pulmonary cytochrome P450 (P450) system t o increase at 48 h after the exposure. However, the most pronounced effect of hyperoxia was observed on pulmonary ethoxycoumarin O-deethylase and etho xyresorufin O-deethylase activities which were induced 4- and 25-fold respe ctively after 48 h. III the liver, P450 and NADH b(5) reductase were increa sed after 48 h, while other components of the monooxygenase system remained unchanged. In the hepatic microsomes, contrary to the lungs, aminopyrine N -demethylase activity was decreased after 24 h of hyperoxic exposure (P < 0 .05) and returned to the control level by 48 h. Similar changes were observ ed in benzphetamine N-demethylase activity. Aniline hydroxylase activity wa s decreased after 8 h of hyperoxic exposure (P < 0.01) and remained decreas ed at 24 h (P < 0.01) and 48 h (P < 0.05). The level of induction of ethoxy coumarin O-deethylase and ethoxyresorufin O-deethylase activities, however, was almost similar in the liver to that observed in the lungs.