CCl4-Induced Cytochrome P-450 Loss and Lipid Peroxidation in Rat Liver Slices
Previous studies from this laboratory have shown a concentration-time dependent, site specific cytotoxicity of CCl4 in slices. The present study examined radical formation and lipid peroxidation as a potential mechanism of toxicity. Liver slices from male Sprague-Dawley rats (220– 250 g) were exposed to 0.57 mM CCl4 by vaporization using a roller incubation system. Cytochrome P-450 is responsible for the bioactivation of CCl4 generating the CCl3 radical, which also acts as a suicide inhibitor. In slices exposed to CCl4, cytochrome P-450 loss occurred in a timedependent manner relative to controls (↓ 58% at 9 hr). A 48 hr fast prior to sacrifice both enhanced and accelerated both cytochrome P-450 loss as well as CCl4 toxicity in slices. Unlike cytochrome P-450, glutathione levels were not altered over the course of the experiment. These studies suggest that centrilobular hepatocytes are more susceptible to CCl4 induced injury. Covalent binding studies using 14CC14 confirmed CCl3 radical formation by cytochrome P-450. Binding to slice proteins plateaued as early as 30 min following CCl4 administration whereas lipid binding was saturated by 60 min. Covalent binding of the CCl3 radical was increased two-fold 60 min following phenobarbital pretreatment whereas allylisopropylacetamide caused the converse (50% at 60 min). Conjugated diene formation, an index of lipid peroxidation as detected by 15 min following
KeywordsCovalent Binding Liver Slice CCl3 Radical Conjugate Diene Formation Trichloromethyl Radical
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