Graduate Thesis Or Dissertation
 

Alterations in mink reproductive physiology following exposure to coplanar and noncoplanar polychlorinated biphenyls (PCBs)

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  • Female mink (Mustela vison) are highly sensitive to polychlorinated biphenyl (PCB)-induced reproductive impairment. The goal of this research was to develop a better understanding of the mechanism of PCB-induced effects on female mink, mink embryos, and surviving mink kits. Anestrous, juvenile female mink and pregnant, adult mink were exposed to 3,3',4,4',5,5'-hexachlorobiphenyl (3HCB), a coplanar PCB, or 2,2',4,4',5,5'-hexachlorobiphenyl (2HCB), a noncoplanar PCB. During anestrus or at the onset of implantation, female mink received intraperitoneal injections of 0.4 or 0.8 mg 3HCB/kg, 20 mg 2HCB/kg, corn oil (CO), or no treatment. Anestrous females were treated with 1713-estradiol for 24 h prior to analysis. In the second experiment, CO-exposed animals received empty silastic implants, while 3HCB-treated mink received either empty or progesterone (P)-filled implants. Weights were similar between treatment groups in the first experiment, but in the second study, 3HCB-treated females lost as much as 10 % of their body weight. Hepatic not 2HCB. Both congeners impaired 17β-estradiol-stimulated up-regulation ofuterine nuclear estrogen receptors (ER) in anestrous mink. Embryotoxicity and reduced embryo growth were observed 14 days after exposure to 0.4 mg 3HCB/kg > 0.8 mg 3HCB/kg > 20 mg 2HCB/kg. In pregnant mink, all 3 HCB treatments decreased progesterone receptor (PR) affinity. ER concentration and cytosolic PR total receptor number (Rt) were significantly increased by 20 mg 2HCB/kg > 0.8 mg 3HCB/kg. No significant difference was observed in either the total number or affinity of PR between in vitro systems with or without 3HCB. From day 10 forward, implantation sites from 3HCB-treated mink contained necrotic tissue from resorbing embryos. Progesterone treatment did not prevent resorption, but increased uterine prolactin receptor concentration. Length of rib, ulna, tibia, and fibula and diameter of humerus were found to be significantly reduced in day 1 kits exposed to 2HCB in ?hero. We conclude that PCBs are antiestrogenic in anestrous females and antiprogestational in pregnant mink, but reduced PR affinity is not the proximate cause of embryo resorption. In addition, 2HCB produces estrogenic changes in bones of mink embryos.
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