Impaired Maturation, Fertilization, and Embryonic Development of Porcine Oocytes Following Exposure to an Environmentally Relevant Organochlorine Mixture1

The reproductive health risks related to exposure to persis-tent organic pollutants in the environment remain controversial. This debate is partly because most studies have investigated only one or two chemicals at a time, whereas populations are ex-posed to a large spectrum of persistent chemicals in their en-vironment. Using the pig as a toxicological model, we hypoth-esized that exposing immature cumulus-oocyte complexes to an organochlorine mixture during in vitro maturation (IVM) would adversely affect oocyte maturation, fertilization, and subsequent embryo development. This organochlorine mixture mimics that which contaminates the Arctic marine food chain. Cumulus-oo-cyte complexes were cultured in IVM medium containing in-creasing concentrations of the organochlorine mixture, similar to that found in women of highly exposed populations. Organ-ochlorines reduced the quality of cumulus expansion and the viability of cumulus cells in a dose-response manner. The pro-portion of apoptotic cumulus cells also increased due to organ-ochlorine exposure. Half of the oocytes were fixed after insem-ination, and the remainders were cultured for 8 days. Concen-trations of organochlorines did not affect the rates of oocyte degeneration, sperm penetration, and development to morula. However, incidence of incompletely matured oocytes increased and polyspermy rate decreased, both in a dose-response manner with increasing organochlorine concentrations. Blastocyst for-mation and number of cells per blastocyst declined with organ-ochlorine concentration. Exposing porcine cumulus-oocyte complexes to an environmentally pertinent organochlorine mix-ture during IVM disturbs oocyte development, supporting recent concerns that such pollutants harm reproductive health in hu-mans and other mammalian species. cumulus cells, embryo, in vitro fertilization, oocyte development, toxicolog