MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(FOR-1116-627498) Inhibition of Oocyte Maturation in Xenopus by Polybrominated Diphenyl Ethers, Perfluorooctane Sulfonate, and Perfluorooctanoic Acid.

Fort, D¹, Rogers, R¹, Thomas, J¹, Guiney, P², Weeks, J², ¹ Fort Environmental Laboratories, Stillwater, OK, USA² SC Johnson & Son, Racine, WI, USA

ABSTRACT- Under normal conditions, Xenopus oocytes undergo final maturation which is induced by progesterone via a membrane bound receptor (OMPR) or androgens via a classical intracellular receptor (AR). Final maturation is marked morphologically by germinal vesicle breakdown (GVBD). The anti-progestin and anti-androgen activities of a series of persistent halogenated substituted polybrominated diphenyl ethers (BDEs) including: pentabromodiphenyl ether (PBDE) [DE-71], octabromdiphenyl ether (OBDE), and decabromodiphenyl ether (DBDE); and the ubiquitous perfluorochemicals (PFCs), perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were screened using an in vitro Xenopus oocyte GVBD assay. Results suggested that each of the BDEs, but not PFOS or PFOA inhibited progesterone-induced GVBD in vitro in a concentration-dependent manner. BDE potency for progesterone-induced GVBD, expressed as an IC25, ranged from 0.08 ug/L for PBDE to 8.45 ug/L for DBDE. PFOS, PFOA, and to a lesser extent PBDE, inhibited androstenedione-induced GVBD with potencies (IC25) ranging from 1.98 ug/L for PFOS to 8.14 ug/L for PBDE. Radioreceptor binding studies with isolated OMPR indicated that inhibition of progesterone-induced GVBD was proportional to BDE binding affinity for the OMPR. These results suggested that the inhibitory effects of the BDEs on GVBD may be mediated primarily through the OMPR, whereas, the inhibitory nature of PFOS and PFOA is postulated to be a result of inhibition of the AR pathway. Furthermore, the inhibitory potency of the BDEs appeared to be inversely related to the degree of bromination of each mixture. Ultimately, these results suggested that these substances were capable of interfering with endocrine systems and reproductive processes in amphibians.

Key words: brominated diphenyl ethers, PFOS, PFOA, reproductive toxicity