THE PHYTOESTROGEN BETA-SITOSTEROL ALTERS THE REPRODUCTIVE ENDOCRINE STATUS OF GOLDFISH

There is growing awareness that chemicals in the environment may funct ion as hormone mimics and affect endocrine function in wildlife. In th is study, the effects of beta-sitosterol, a phytoestrogen present in h igh concentration in bleached kraft pulp mid effluent (BKME), on repro ductive fitness of goldfish were investigated. Plasma reproductive hor mone levels were measured in male and female goldfish on Day 4 followi ng two intraperitoneal injections of beta-sitosterol or an oxidized si tosterol preparation. In some experiments, plasma hormone levels were also measured after fish were injected with Ovaprim, which contains a superactive analog of salmon GnRH and the dopamine receptor antagonist domperidone and leads to increased secretion of gonadotropin (GtH)-II (LH-type GtH). Plasma testosterone (T) and 11-ketotestosterone levels in males and T and 17 beta-estradiol levels in females were significa ntly decreased in beta-sitosterol-treated fish on Day 4 and 24 hr afte r an injection of Ovaprim. Plasma GtH-II levels were elevated in male fish treated with beta-sitosterol on Day 4 and further increased in re sponse to Ovaprim, suggesting that reduced plasma steroid levels were not due to effects on pituitary function. In other studies, testes pie ces from beta-sitosterol-treated goldfish produced reduced levels of T and pregnenolone in vitro both basally and in response to the GtH-II agonist human chorionic gonadotropin (hCG) when compared to the testes from control fish. Basal and hCG-stimulated pregnenolone and hCG-stim ulated T were reduced in follicles from beta-sitosterol-treated fish; however, basal T production was not different from controls. These res ults suggest that beta-sitosterol reduces the gonadal steroid biosynth etic capacity through effects on cholesterol availability or the activ ity of the side chain cleavage enzyme P-45OSCC. These findings raise t he possibility that beta-sitosterol could be a contributing factor to the reproductive dysfunction observed in fish exposed to BKME. (C) 199 5 Academic Press, Inc.