Adverse reproductive effects in male fathead minnows (Pimephales promelas) exposed to environmentally relevant concentrations of the natural oestrogens, oestradiol and oestrone

Recent research has shown that low concentrations of natural and synthetic oestrogens are present in sewage treatment works effluents. However, the effects of these oestrogens on fish, at environmentally relevant concentrations, are unknown. Therefore, male fathead minnows (Pimephales promelas) were exposed to nominal concentrations of 17 beta-oestradiol (10, 32, 100, 320 and 1000 ng l(-1)) and molar equivalent concentrations of oestrone (9.9, 31.8, 99.3, 318 and 993 ng l(-1)) for 21 days, to determine the effects of these chemicals on plasma vitellogenin levels and gonad weight. Exposure to both steroidal compounds resulted in an elevation of plasma vitellogenin levels, in a concentration-related manner. Significant (P < 0.01) increases were obtained at and > 100 ng oestradiol l(-1) and 31.8 ng oestrone l(-1). This increase in plasma vitellogenin levels was accompanied by an inhibition of testicular growth, which for the highest two concentrations of oestradiol was total. The results from this study indicated that although oestrone induced significant effects at a lower concentration, oestradiol was more potent than oestrone at higher concentrations, causing greater vitellogenin synthesis and testicular inhibition. The key result is that low concentrations of oestradiol and oestrone, similar to the reported concentrations in effluent, have profound effects on male fish. (C) 1998 Elsevier Science B.V. All rights reserved.