Impaired maturation, fertilization, and embryonic development of porcine oocytes following exposure to an environmentally relevant organochlorine mixture

The reproductive health risks related to exposure to persistent organic pol lutants in the environment remain controversial. This debate is partly beca use most studies have investigated only one or two chemicals at a time, whe reas populations are exposed to a large spectrum of persistent chemicals in their environment. Using the pig as a toxicological model, we hypothesized that exposing immature cumulus-oocyte complexes to an organochlorine mixtu re during in vitro maturation (IVM) would adversely affect oocyte maturatio n, fertilization, and sub sequent embryo development. This organochlorine m ixture mimics that which contaminates the Arctic marine food chain. Cumulus -oocyte complexes were cultured in IVM medium containing increasing concent rations of the organochlorine mixture, similar to that found in women of hi ghly exposed populations. Organochlorines reduced the quality of cumulus ex pansion and the viability of cumulus cells in a dose-response manner. The p roportion of apoptotic cumulus cells also increased due to organochlorine e xposure. Half of the oocytes were fixed after insemination, and the remaind ers were cultured for 8 days. Concentrations of organochlorines did not aff ect the rates of oocyte degeneration, sperm penetration, and development to morula. However, incidence of incompletely matured oocytes increased and p olyspermy rate decreased, both in a dose-response manner with increasing or ganochlorine concentrations. Blastocyst formation and number of cells per b lastocyst declined with organochlorine concentration. Exposing porcine cumu lus-oocyte complexes to an environmentally pertinent organochlorine mixture during IVM disturbs oocyte development, supporting recent concerns that su ch pollutants harm reproductive health in humans and other mammalian specie s.