Impaired Maturation, Fertilization, and Embryonic Development of Porcine Oocytes Following Exposure to an Environmentally Relevant Organochlorine Mixture ¹

Biology of Reproduction v.65, n.2 1aug01

Céline Campagna ^a, Marc-André Sirard ^a, Pierre Ayotte ^b and Janice L. Bailey ^{a, 2}

^a Centre de Recherche en Biologie de la Reproduction,

^b Département des Sciences Animales, and Unité de Recherche en santé Publique (CHUL-CHUQ), Département de Médecine Sociale et Préventive, Université Laval, Sainte-Foy, Québec, Canada G1K 7P4 

ABSTRACT

The reproductive health risks related to exposure to persistent 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 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 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-oocyte complexes were cultured in IVM medium containing increasing concentrations of the organochlorine mixture, similar to that found in women of highly exposed populations. Organochlorines reduced the quality of cumulus expansion and the viability of cumulus cells in a dose-response manner. The proportion of apoptotic cumulus cells also increased due to organochlorine exposure. Half of the oocytes were fixed after insemination, and the remainders were cultured for 8 days. Concentrations 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 formation and number of cells per blastocyst declined with organochlorine concentration. Exposing porcine cumulus-oocyte complexes to an environmentally pertinent organochlorine mixture during IVM disturbs oocyte development, supporting recent concerns that such pollutants harm reproductive health in humans and other mammalian species. 

FOOTNOTES
First decision: 26 February 2001. 

1 This work was supported by the Toxic Substance Research Initiatives Programme of Health Canada. 

2 Correspondence: J.L. Bailey, Centre de Recherche en Biologie de la Reproduction, Départment des Sciences Animales, Pavillon Comtois, Université Laval, Sainte-Foy, PQ, Canada G1K 7P4. FAX: 418 656 3766; janice.bailey@crbr.ulaval.ca