Recovery of ovary size, follicle cell apoptosis, and HSP70 expression in fish exposed to bleached pulp mill effluent

We hypothesized that impaired ovarian function (e.g., reduced ovary size) in wild fish chronically exposed to bleached pulp mill effluents is related to an increased rate of apoptosis in ovarian follicle (granulosa and (or) theca) cells. In 1996, vitellogenic white sucker (Catostomus commersoni) collected downstream of a bleached kraft pulp mill had reduced ovary size associated with increases in ovarian cell apoptosis and stress protein (HSP70) expression when compared with fish collected from an upstream reference site. Fish sampling was repeated in 1998 following mill maintenance changes aimed at minimizing the discharge of process chemicals. In 1998, there were no differences in ovary size, ovarian cell apoptosis, or ovarian HSP70 levels between fish collected upstream and downstream of the mill. Based on the results of this and our previous work, we conclude that chronic stimulation of ovarian cell apoptosis by certain components of mill effluents may represent an important cellular mechanism responsible for reductions in ovary size, and potentially other integrated reproductive responses, in female fish exposed to pulp mill effluents.