Effects of waterborne exposure of 17 beta-estradiol on secondary sex characteristics and gonads of fathead minnows (Pimephales promelas)

Environmental contaminants with estrogenic activity have recently received attention because of their potential effects on the reproductive efficiency of humans and wildlife. This study was conducted with the endogenous estro gen, 17 beta-estradiol (E2), to establish the histologic response of the fa thead minnow (Pimephales promelas) as a model organism. Sexually mature fat head minnows were exposed for 14 days to waterborne concentrations of 1000, 100, 10, 2, 1, 0.5, 0.25, 0.125, 0.1 or 0.0625 nM E2. Exposure to E2 cause d a reduction in size of the prominent male secondary sex characteristics, the fatpads and nuptial breeding tubercles. Histological lesions observed i n the testes included proliferation of Sertoli cells and degenerative chang es. Electron microscopy of seminiferous tubules and their Sertoli cells rev ealed large phagolysosomes filled with degenerating spermatozoa and other c ellular debris. Females had ovaries in which most of the follicles were in the primary stage of development. There were also more atretic follicles an d fewer secondary and Graafian follicles than in unexposed females. These f indings demonstrate components of sexually mature fish which may be altered by compounds that mimic E2. To determine if lesions observed in males were permanent, 50 sexually mature males and females were exposed to a single c oncentration of 10 nM E2 for 10 days. Samples were collected from males on the final day of E2 exposure and over a period of 16 weeks after the exposu re was stopped. No E2-induced lesions were observed beyond 16 weeks post E2 exposure. Results of these studies suggest that histological lesions could occur at ecologically-relevant exposures to 'estrogenic' compounds. Howeve r, certain lesions caused by exposure of adult fathead minnows are not perm anent. (C) 1999 Elsevier Science B.V. All rights reserved.