Induction of cytochrome P-450 isozymes in liver microsomes of rats treated with the cardiotonic agent sulmazole.

Pretreatment of adult male rats with sulmazole (AR-L 115 BS) results in a 2-6-fold increase of the liver microsomal scoparone O-demethylation and 7-ethoxycoumarin O-deethylation activity. The change in the ratio of the demethylation products scopoletin to isoscopoletin from 1 : 1.8 +/- 0.1 in control microsomes to 1: 2.5 +/- 0.1 in microsomes from sulmazole pretreated rats is statistically significant. Sulmazole produces a modified type II difference spectrum when added to microsomes of control or sulmazole-pretreated rats. Immunoquantitation of seven cytochromes P-450 showed that two forms, namely P-450 beta NF/ISF-G and P-450 beta NF-B, are increased 3-4-fold in the microsomes of sulmazole-pretreated rats.