Metabolic activation of carcinogenic diethylstilbestrol in rodents and humans.

In vivo biotransformation of diethylstilbestrol (DES) was studied by radio-GLC and GLC-mass spectrometry using both radioactively and deuterium-labeled DES. Among the urinary and biliary metabolites identified in intact Wistar rat and Syrian golden hamsters are dienestrol and hydroxy and methoxy derivatives of dienestrol and DES. The identification of 4'-hydroxypropiophenone as a urinary metabolite of DES in the rat is consistent with the hypothesis that dienestrol is formed via an epoxide-diol pathway. Some of the metabolites imply electrophilic reactivity according to their chemical structure and may represent proximate carcinogens of DES. In humans, dienestrol and hydroxy dienestrol constitute the major urinary DES metabolites in men and were also identified in the urine of a woman. Considerable species differences in DES metabolism between humans and rats were found with regard to the route of excretion and the pattern of urinary metabolites.