| 6860371 |
Newman SL, Guzelian PS: Identification of the cyanopregnenolone-inducible form of hepatic cytochrome P-450 as a catalyst of aldrin epoxidation. Biochem Pharmacol. 1983 May 1;32(9):1529-31.
In light of recent suggestions that hepatic microsomal aldrin expoxidation activity selectively reflects the phenobarbital (PB)-inducible form (s) of cytochrome P-450 (P-450PB), we tested the effect of pregnenolone-16 alpha-carbonitrile (PCN), a synthetic steroid that induces P-450PCN, a form of the cytochrome biochemically and immunochemically distinguishable from P-450PB. In hepatic microsomes prepared from rats receiving PB, 3-methylcholanthrene (3-MC), or PCN, the latter compound produced a greater increase in aldrin epoxidation activity relative to control than did PB, whereas 3-MC decreased enzyme activity. Moreover, the aldrin epoxidation activity in microsomes prepared from PCN- or PB-pretreated rats was selectively inhibited by form-specific antibodies directed against P-450PCN or P-450PB, respectively, whereas anti-P-450MC antibodies gave no inhibition with microsomes prepared from induced or control animals. We conclude that P-450PCN, P-450PB, and probably other cytochromes P-450 catalyze aldrin epoxidation, precluding use of this enzyme as a specific marker of a single form of the cytochrome. |
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