| Abstrakt: |
Wild fish exposed to bleached kraft-mill effluent (BKME) have a variety of reproductive dysfunctions. BKME contains _-sitosterol, a presumed phytoestrogen. In this study, goldfish were exposed for 12 d to concentrations of _-sitosterol typical of BKME (75, 300, 600, and 1,200 5 g/L) and to 17beta-estradiol (E2) (75 and 300 5 g/L) for comparative purposes. In general, plasma reproductive steroid levels in males and females were decreased by _-sitosterol treatment. E2 exposure significantly increased plasma steroid levels. Basal in vitro production of testosterone (T) and pregnenolone by testes of _-sitosterol-treated fish were either unchanged or decreased, while human chorionic gonadotropin (hCG)- stimulated T and pregnenoloneproduction were decreased. 25-OH Cholesterol treatment stimulated only pregnenolone production. In E2-treated fish, basal, hCG- and 25-OH cholesterol- treated testes had either unchanged or increased T and pregnenolone production. Steroids ofbeta-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 _-sitosterol treatment. In E2-treated fish, plasma GtH-II levels were decreased; plasma GtH-II following Ovaprim injection was unchanged.Gonadal cholesterol levels were decreased in the 1,200-5 g/L _-sitosterol-treated fish but were unchanged in E2-treated fish. These results suggest that decreases in plasma steroids by _-sitosterol are possibly due to alterations in cholesterol availability to P450scc (enzyme that converts cholesterol to pregnenolone) orP450scc activity. _-Sitosterol also appears to affect gonadal steroidogenesis between pregnenolone and T. These findings strengthen the suggestion that _-sitosterol could be a contributing factorto the reproductive dysfunctions observed in BKME-exposed fish. [ABSTRACT FROM AUTHOR] |
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