[Use of human liver biopsy samples as a technique for evaluation of cytochrome P-450].

Liver cytochromes-P450 are of primary importance in the metabolism of numerous drugs. Their activity is modulated by exogenous factors such as drug treatment. The parameters of human oxidase metabolism were determined "in vitro" in order to evaluate the activity of a specific monooxygenase (benzopyrene hydroxylase). Substances capable of modulating monooxygenase function were identified. This may be useful to predict drug-Cyt-P450 interaction "in vivo". The hydroxylation of benzopyrene in human microsomes prepared from human liver samples (biopsies) was used as a model to study the treatment effect on cytochrome-P450. The kinetic parameters of this reaction are stable and reproducible (Km = 1.37 +/- 0.35 microM, Vmax = 0.49 +/- 0.03 nmole 30 H-BP/min/ nmole CYT-P450). The Michaelis-Menten values are given by mean +/- standard deviation.