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Characterization of Drug Metabolism Enzymes in Estrogen-induced Kidney Tumors in Male Syrian Hamsters¹

Department of Pharmacology and Toxicology, The University of Texas Medical Branch, Galveston, Texas 77550-2774

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 -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.

¹ Supported by grants from the USPHS, National Cancer Institute (CA43232 and CA43233).

² To whom requests for reprints should be addressed.

Received 3/11/88. Revised 6/14/88. Accepted 7/15/88.

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