Exposure to beta-sitosterol alters the endocrine status of goldfish differently than 17 beta-estradiol

Wild fish exposed to bleached kraft-mill effluent (BKME) have a variety of reproductive dysfunctions. BKME contains beta-sitosterol, a presumed phytoestrogen. In this study, goldfish were exposed for 12 d to concentrations of beta-sitosterol typical of BKME (75, 300, 600, and 1,200 mu g/L) and to 17 beta-estradiol (E-2) (75 and 300 mu g/L) for comparative purposes. In general, plasma reproductive steroid levels in males and females were decreased by beta-sitosterol treatment. E-2 exposure significantly increased plasma steroid levels. Basal in vitro production of testosterone (T) and pregnenolone by testes of beta-sitosterol-treated fish were either unchanged or decreased, while human chorionic gonadotropin (hCG)-stimulated T and pregnenolone production were decreased. 25-OH Cholesterol treatment stimulated only pregnenolone production. rn E-2-treated fish, basal, hCG- and 25-OH cholesterol treated testes had either unchanged or increased T and pregnenolone production. Steroids of beta-sitosterol fish increased in response to Ovaprim (salmon GnRH and the dopamine receptor antagonist domperidone) to a lesser degree than in control fish. Overall, gonadotropin II (GtH-II) levels were not changed by beta-sitosterol treatment. In E-2-treated fish, plasma GtH-II levels were decreased; plasma GtH-II following Ovaprim injection was unchanged. Gonadal cholesterol levels were decreased in the 1,200-mu g/L beta-sitosterol-treated fish but were unchanged in E-2-treated fish. These results suggest that decreases in plasma steroids by beta-sitosterol are possibly due to alterations in cholesterol availability to P-450scc (enzyme that converts cholesterol to pregnenolone) or P-450scc activity. beta-Sitosterol also appears to affect gonadal steroidogenesis between pregnenolone and T. These findings strengthen the suggestion that beta-sitosterol could be a contributing factor to the reproductive dysfunctions observed in BKME-exposed fish.