Exposure to bleached kraft pulp mill effluent reduces the steroid biosynthetic capacity of white sucker ovarian follicles

White sucker exposed to bleached kraft mill effluent (BKME) show a number of reproductive alterations correlated to reduced circulating reproductive steroid levels. The purpose of this experiment was to examine the steroid biosynthetic capacity of white sucker ovarian follicles undergoing vitellogenesis to determine if reductions in steroid production contribute to the reduced circulating steroid levels found during this stage of reproduction. We also examined the mechanisms responsible for steroid production within the ovary to determine where BKME exerts its impacts. Follicles collected from BKME-exposed fish during early and late vitellogenesis had reduced testosterone and 17β-extradiol production under basal and human chorionic gonadotropin stimulated conditions. Production of cyclic 3′,5′ adenosine monophosphate (cAMP) by ovarian follicles was similar between sites suggesting impacts occurred post-cAMP formation. Reduced conversion of exogenous testosterone to 17β-estradiol during August collections demonstrates reduced levels of the aromatase enzyme in BKME-exposed follicles during early vitellogenic stages. Measurement of pregnenolone production in October indicates similar P450 side chain cleavage enzyme activity between sites, suggesting disruptions downstream of pregnenolone formation were responsible for the reduced steroid productivity in ovarian follicles from BKME-exposed fish during this stage of the reproductive cycle.