Selective induction of cytochrome b 5 and NADH cytochrome b 5 reductase by propylthiouracil

Abstract

Both the cytochrome b 5 level and NADH cytochrome b 5 reductase activity in rat liver microsomes were increased 2-fold by repeated i.p. administration of 1.5 mmol/kg propylthiouracil (PTU) for 2 weeks, but neither the cytochrome P-450 level nor NADPH cytochrome P-450 reductase activity were affected by the treatment. Liver microsomes from PTU-treated rats showed a significant decrease in aminopyrine N-demethylation, but not in benzphetamine N-demethylation, aniline hydroxylation or 7-ethoxycoumarin O-deethylation. A single administration of the compound had no effect on any components of the system. In vitro , drug hydroxylation activities were not affected by PTU up to 1.0 mM. From the above evidence, repeated administration of PTU selectively induced cytochrome b 5 and NADH cytochrome b 5 reductase in rat liver microsomes.