A form of human hepatic microsomal cytochrome P-450 (P450hA7) with subunit Mr 50,400 has been purified from an epileptic who had been receiving long-term treatment with anticonvulsant drugs. P450hA7 metabolized the immunosuppressant drug cyclosporin A and the dihydropyridine calcium channel antagonist nifedipine, but did not metabolize a similar dihydropyridine drug, nicardipine, nor a series of alkoxyresorufin model substrates. The hepatic microsomal concentration of P450hA7 was higher in five individuals who had been receiving long-term anticonvulsant treatment than in any of 21 individuals who had not been similarly treated. The mean P450hA7 concentration in the treated individuals was 5-fold higher than the mean concentration in the untreated individuals. It is concluded that P450hA7 is a member of the cytochrome P450III family which is induced by anticonvulsant drugs in man.
Purification and characterization of an anticonvulsant-induced human cytochrome P-450 catalysing cyclosporin metabolism
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P M Shaw, T S Barnes, D Cameron, J Engeset, W T Melvin, G Omar, J C Petrie, W R Rush, C P Snyder, P H Whiting, C R Wolf, M D Burke; Purification and characterization of an anticonvulsant-induced human cytochrome P-450 catalysing cyclosporin metabolism. Biochem J 1 November 1989; 263 (3): 653–663. doi: https://doi.org/10.1042/bj2630653
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