ESTROGEN METABOLISM IN MICROSOMAL, CELL, AND TISSUE PREPARATIONS OF KIDNEY AND LIVER FROM SYRIAN-HAMSTERS

The estrogen-treated golden Syrian hamster has been used as an experim ental model for estrogen-induced and estrogen-dependent cancers, but p athways to neoplastic transformation remain unknown in this animal. Me tabolism 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 different in vitro preparations from untreated and estrogen-treated Syrian hamsters, primary kidney cell cu ltures, microsomal preparations, and freshly prepared tissue kidney sl ices. In primary kidney cell cultures, the amount of catechol estrogen s decreased upon increasing estrogen (DES) treatment period, and compl etely disappeared after about 6 months treatment. This decrease is not a result of formation of less amounts of catechol estrogens, but rath er reflects the presence of the enzyme systems to further metabolize a ny formed catechol estrogens, since the amount of catechol estrogens f ormed, as detected by (H2O)-H-3 release, is unchanged. The polar metab olites 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 metho xyestrogens were isolated. Studies of estradiol metabolism in microsom al preparations showed a very low rate of metabolism, compared to the primary kidney cell cultures. In contrast, estrogen metabolism was ext ensive in kidney slices from untreated hamsters, with only approx. 30% of the substrate estradiol remaining unmetabolized after 6 h of incub ation. While no catechol estrogens were detected, a small quantity of estriol, and a large amount of estrone and methoxyestrogens were isola ted. The polar metabolite a was the main polar metabolite detected, wi th very little of metabolite b and no metabolite c. In kidney slices f rom 4 month DES-treated hamsters, a much higher amount of polar metabo lites was detected, and metabolite c appeared after 6 h incubation. Ma ss spectrometric analysis and HPLC data of metabolite c indicate that this metabolite is 15 alpha-hydroxyestradiol. This metabolite may serv e as a biomarker for changes occurring in the hamster kidney cells und er continuous estrogen exposure. Finally, formation of water soluble c onjugates was demonstrated in both kidney slices and liver slices from Syrian hamsters, with glucuronide, sulfate and thioether conjugates o f estrone and estradiol and glucuronides of catechol estrogens detecte d. The extent of estrogen metabolism observed in the kidney preparatio ns from estrogen-treated hamsters includes increases in the formation of 15 alpha-hydroxyestradiol and other polar metabolites. Furthermore, investigations of estrogen metabolism in kidney tissue slices demonst rate lowered conjugative pathways important for secondary metabolism. The decreased steroid conjugation in the estrogen-treated hamster kidn ey results in greater availability of estrogen metabolites for partici pation in the formation of potentially damaging reactive species and e nhanced oxidative stress in the kidney.