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Abstract
The abilities of various doses of 3,3′,4,4′,5-pentachlorobiphenyl (PCB126) to induce changes in antioxidant enzyme activities and glutathione levels in the brain tissues of rats were examined after subchronic exposure. Groups of rats were administered 10, 30, 100, 300, 550, or 1000 ng PCB 126 kg−1 day−1, p.o., for 13 weeks and the activities of supeoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), as well as glutathione (GSH) levels were determined in the brain tissue homogenates. Treatment resulted in significant and dose-dependent increases in the activities of the three tested enzymes. While maximal increase in GSH-Px activity was achieved with a dose of 100–175 mg kg−1 day−1, CAT and SOD activities continued to increase in response to maximal dose used for this study. On the other hand, GSH levels were suppressed significantly in a dose-dependent fashion. Data suggest that previously observed increase in oxidative stress production by PCB-126 in the brain tissues of rats is associated with dose-dependent rise in antioxidant enzyme activities and GSH depletion. However, the increases in the antioxidant enzyme activities cannot provide full protection against oxidative damage induced by the same doses. In addition, GSH depletion plays a critical role in the previously observed oxidative stress in response to this compound.
Acknowledgments
This study was supported by a grant (# 1 R03 ES09456-01) from the National Institutes of Health/the National Institute of Environmental Health Sciences (NIEHS). Tissues from treated animals were provided to us by Batelle Laboratories (Columbus, Ohio), according to an NIEHS contract (N01-ES-75411) with those laboratories.