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Abstract

The effect of cocaine on heat shock protein (hsp) induction in murine liver was examined using Western blotting and immunohistochemistry. A single dose of cocaine (50 mg/kg, intraperitoneal [i.p.]) was administered to naive, phenobarbital (PB)-induced or β-naphthoflavone (βNF)-induced mice, and the level of hsps in the liver analyzed 3, 6, and 24 hours after the cocaine dose. As measured by Western blotting, hsp70i levels were increased at all time points, and hsp25 levels at the 6- and 24-hour time points. Levels of hsp60, hsc70, and hsp90 remained unchanged. Pretreatment of mice with the cytochrome P-450 inhibitor SKF-525A eliminated both cocaine hepatotoxicity and the induced accumulation of hsp25 and hsp70i. Immunohistochemical localization of hsp25 and hsp70i in the liver showed that concentrations of both hsps were elevated only in cells with altered morphology. As has been observed previously, hepatic enzyme induction with PB or βNF shifted the location of the necrotic lesion within the lobule from zone 2, as observed in naive mice of this strain, toward zone 1 (PB) or zone 3 (βNF), respectively. Localization of induced accumulation of hsp25 and hsp70i was found to shift within the lobule in parallel with the necrotic lesion in these animals. Immunostaining of cocaine reactive metabolites bound to proteins was superimposable on the areas with hsp accumulation and cells with altered morphology. Our observations indicate a strong spatial correlation within the lobule between cocaine reactive metabolite formation, induced accumulation of hsp25 and hsp70i, and cytotoxicity (necrosis).