Acute response of rat liver microsomal lipids, lipid peroxidation, and membrane anisotropy to a single oral dose of polybrominated biphenyls

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Abstract
Liver microsomal lipids and lipid peroxidation activities were examined in adult male rats at intervals over 2 mo. after the administration of a single oral dose of 0 or 500 mg/kg FireMaster BP-6 in corn oil. Microsomal lipids were markedly altered in the polybrominated biphenyl- (PBB-) dosed animals at the earliest time examined (1 wk), and these changes persisted throughout the remainder of the study. An early decrease in the cholesterol-phospholipid ratio was noted, which probably contributed to the significant decrease in the steady-state fluorescence anisotropy demonstrable in intact microsomes and in liposomes prepared from microsomal lipid extracts. Significant concentrations of PBB were present in dosed rat microsomes, but the changes in anisotropy appeared to result from membrane lipid alterations rather than from a direct perturbation by PBB. Iron ascorbate-induced peroxidation was also enhanced in dosed rat microsomes, even when rats were maintained on a low-Fe (25 ppm) diet. These early alterations in membrane fluidity and peroxidative capacity of microsomes may have ultimately contributed to the hepatotoxicity of PBB.