Metabolic activation of diethylstilbestrol: Indirect evidence for the formation of a stilbene oxide intermediate in hamster and rat

Abstract

The synthetic estrogen diethylstilbestrol (DES) has been associated with the occurrence of vaginal and cervical tumors in young women whose mothers had received DES medication during pregnancy (1,2). Among the data available for the carcinogenic activity of DES in animals (3), the high incidence of renal tumors in male hamsters is evident (4,5). Furthermore, binding of DES to tissue macromolecules has been related to hepatic centrolobular necrosis. It has been shown by in vitro experiments that this binding requires a reactive intermediate generated from DES by a cytochrome P-450 dependent oxidation (6,7). Studies carried out in our laboratory about the biotransformation of carcinogenic trans-4-dimethylaminostilbene and its inactive cis-isomer revealed that epoxidation of the stilbene double bond represents a major pathway for the in vivo metabolism of stilbene amine derivatives (8). Since an epoxide of DES as a reactive intermediate metabolite could possibly account for the toxic properties, we are presently investigating the in vivo metabolism of DES in laboratory animals. In this communication we wish to report the identification of six new metabolites from urine and bile of hamster and rat, some of which can be taken as evidence for the metabolic epoxidation of the stilbene double bond in DES. The study was carried out using a mixture of [G-3H]-DES obtained from the Radiochemical Centre Amersham and [monoethyl-l.2-2H5] -DES prepared from perdeutero-ethanol in this laboratory by a modification of the methods of Dodds and Kuwada (9,10). Male Syrian golden hamsters (150-200 g body wt.) and female Wistar rats (200-250 g body wt.) were injected i.p. with 50 mg/kg [3H,2H]-DES dissolved in 0.5 ml of propane-l,2-diol. Urine was collected in 24-hour periods for 5 days and stored at -20°C. Bile was obtained from unanesthesized cannulated