Estrogen metabolism in microsomal, cell, and tissue preparations of kidney and liver from Syrian hamsters.

Abstract The estrogen-treated golden Syrian hamster has been used as an experimental model for estrogeninduced and estrogen-dependent cancers, but pathways to neoplastic transformation remain unknown in this animal. Metabolism of estrogens to activated or reactive compounds, followed by subsequent oxidative damage to the target tissue, remains a potential step in the tumorigenic process. In this study, the extent of estrogen metabolism is compared in three differentin vitro preparations from untreated and estrogen-treated Syrian hamsters, primary kidney cell cultures, microsomal preparations, and freshly prepared tissue kidney slices. In primary kidney cell cultures, the amount of catechol estrogens decreased upon increasing estrogen (DES) treatment period, and completely disappeared after about 6 months treatment. This decrease is not a result of formation of less amounts of catechol estrogens, but rather reflects the presence of the enzyme systems to further metabolize any formed catechol estrogens, since the amount of catechol estrogens formed, as detected by3H2O release, is unchanged. The polar metabolites a, b and c increased with estrogen treatment, and metabolite c appeared only after DES treatment. The appearance of polar metabolite c only in kidney preparations from DES-treated animals implies that it may serve as a marker of cellular transformation. Estriol and estrone were detected, but were not affected by DES treatment, while no methoxyestrogens were isolated. Studies of estradiol metabolism in microsomal preparations showed a very low rate of metabolism, compared to the primary kidney cell cultures. In contrast, estrogen metabolism was extensive in kidney slices from untreated hamsters, with only approx. 30% of the substrate estradiol remaining unmetabolized after 6 h of incubation. While no catechol estrogens were detected, a small quantity of estriol, and a large amount of estrone and methoxyestrogens were isolated. The polar metabolite a was the main polar metabolite detected, with very little of metabolite b and no metabolite c. In kidney slices from 4 month DES-treated hamsters, a much higher amount of polar metabolites was detected, and metabolite c appeared after 6 h incubation. Mass spectrometric analysis and HPLC data of metabolite c indicate that this metabolite is 15α-hydroxyestradiol. This metabolite may serve as a biomarker for changes occurring in the hamster kidney cells under continuous estrogen exposure. Finally, formation of water soluble conjugates was demonstrated in both kidney slices and liver slices from Syrian hamsters, with glucuronide, sulfate and thioether conjugates of estrone and estradiol and glucuronides of catechol estrogens detected. The extent of estrogen metabolism observed in the kidney preparations from estrogen-treated hamsters includes increases in the formation of 15α-hydroxyestradiol and other polar metabolites. Furthermore, investigations of estrogen metabolism in kidney tissue slices demonstrate lowered conjugative pathways important for secondary metabolism. The decreased steroid conjugation in the estrogen-treated hamster kidney results in greater availability of estrogen metabolites for participation in the formation of potentially damaging reactive species and enhanced oxidative stress in the kidney.