Characterization of drug metabolism enzymes in estrogen-induced kidney tumors in male Syrian hamsters.

In an attempt to characterize metabolism enzymes of the estrogen-induced kidney tumor in male Syrian hamsters, the activities of enzymes involved in drug and glutathione metabolism were determined in tumor tissue. Kidney tumors were induced in male Syrian hamsters by treatment with estradiol for 8 months. Cytochrome P-450 and cytochrome b5 concentrations in tumors were below detectable levels. However, when cytochrome P-450-mediated oxidation was analyzed by product formation assays, the oxidation of E-diethylstilbestrol to diethylstilbestrol-4',4"-quinone by tumor microsomes was 10-20% of the rate found in control microsomes. In kidney tissue surrounding estrogen-induced tumors, cytochrome P-450 and b5 contents were 50-60% less than those in untreated kidney. Activities of reducing enzymes of drug metabolism (cytochrome P-450, cytochrome b5 and NADH:cytochrome c reductases), glutathione metabolism enzymes (glutathione peroxidase, glutathione transferase, glutathione reductase, and gamma-glutamyl transpeptidase), and free radical scavenging enzymes (superoxide dismutase, catalase, and quinone reductase) in tumor were significantly lower than in untreated kidney tissue. The activities of these enzymes in renal tumor surrounding tissue were between those observed in tumor and control kidney. Glucose-6-phosphate dehydrogenase activity was increased by 50% in surrounding tissue and 430% in tumor compared to values in untreated controls. The decreased enzyme activity levels in hormone-exposed tissue surrounding tumors likely represented an adaptation of this tissue to the neoplastic environment induced by chronic estrogen treatment.