| Abstract: | Adriamycin treatment in vivo or addition to incubation mixtures in vitro inhibits hepatic drug metabolism. It has been suggested that adriamycin-induced membrane lipid peroxidation may be a mechanism responsible for this activity in vitro. To determine if similar mechanisms operate in vivo, adriamycin inhibition of drug metabolism was compared in rats whose tissue lipid peroxidizability was altered by manipulating dietary levels of vitamin E. Weanling rats maintained on vitamin E deficient (0 ppm) or supplemented (10 or 100 ppm) diets for 12 weeks were given either adriamycin, 5 mg/kg/week, or equal volumes of the saline vehicle for 3 weeks intraperitoneally. Vitamin E deficiency alone (0 ppm, saline pretreatment) produced a 37% increase in hepatic lipid peroxidation without any appreciable alteration in hepatic aniline hydroxylase, ethylmorphine N-demethylase or aryl hydrocarbon hydroxylase activities. Adriamycin pretreatment altered hepatic lipid peroxidizability over corresponding saline pretreated controls dependent on dietary vitamin E. No increase was seen in the 100 ppm group, while 44% and 500% increases occurred at 10 and 0 ppm vitamin E, respectively. Adriamycin pretreatment decreased drug-metabolizing enzyme activity by an average of 32% for aniline hydroxylase, 26% for ethylmorphine N-demethylase and 63% for aryl hydrocarbon hydroxylase. Statistically, decreases in drug metabolism were independent of dietary vitamin E and did not correlate with lipid peroxidizability. These data would suggest that in vivo adriamycin-induced depression of hepatic drug-metabolizing enzymes is not mediated by elevated lipid peroxidation. |
