INDUCTION OF CYTOCHROME-P-450 1A1 IN RAT-LIVER BY ULTRASOUND

Cytochrome P-450-specific monooxygenase activities (androstenedione-hy droxylase and pentoxyresorufin-and ethoxyresorufin-O-dealkylase) were determined in rat liver microsomes after contact ultrasonic treatment of the liver. Androstenedione-hydryoxylase in the liver of ultrasound- treated rats was indistinguishable from the control activity, indicati ng that no induction of CYP2A1, CYP2B1, CYP2C11, CYP3A1(4) occurred. T he O-deethylation rate of the CYP1A1-specific ethoxyresorufin substrat e was 100 pmoles/min per mg in untreated and up to 300 pmoles/min per mg in treated rats. Western-blot analysis revealed CYP1A1 in the liver of ultrasound-treated rats which was absent in untreated rats. The le vel of mRNA for CYP1A1 in the liver of ultrasound treated rats increas ed from 0.5 to 6.0 fmoles of mRNA/mu g RNA, while the corresponding va lue for CYP1A2 remained unchanged. These results show that cytochrome P-450 1A1 can be induced not only by exogenous chemicals, but also by ultrasound.