Cellular and molecular mechanisms mediating the effects of polychlorinatedbiphenyls on oocyte developmental competence in cattle

Polychlorinated biphenyls (PCBs) can interfere with normal reproductive fun ctions acting as endocrine disruptors. Aroclor-1254 (A-1254), is a pool of more than 60 congeners used for in vitro studies because its composition is representative of PCBs environmental pollution. We previously demonstrated that the exposure of bovine oocytes to A-1254 during in vitro maturation ( IVM) was detrimental not only to the maturation process but also induced a significant increase of polyspermy and a reduction of developmental compete nce. Therefore, we investigated whether A-1254 acts on two processes that o ccur during IVM and may be related with its negative effects: maternal mRNA polyadenylation and cortical granules (CGs) migration and exocytosis. Bovi ne cumulus-oocyte complexes (COCs) were exposed to 0.1 mug/ml of A-1254 dur ing IVM, a level of exposure known to affect oocyte maturation, fertilizati on, and developmental competence. Oocyte exposure to A-1254 altered the pol y(A) tail length of 5 out of 10 genes examined. PCBs effect on mRNA polyade nylation was different depending on the gene considered and resulted either in a shorter or in a longer poly(A) tail. At the end of maturation, Aroclo r treated oocytes presented clustered CG in a significantly higher percenta ge than the control group. In addition, CG exocytosis after 8 hr of fertili zation occurred at significantly lower extent in zygotes derived from the e xposed group compared to control. Our results indicated that the lower deve lopmental competence of oocytes exposed to PCBs during IVM can be related t o the interaction of these contaminants with mechanisms regulating maternal mRNA storage in the ooplasm and normal CGs function. Mol. Reprod. Dev. 60: 535-541, 2001. (C) 2001 Wiley-Liss, Inc.