Metabolism of xenobiotics in the human adrenal gland.

The capacity of the human adrenal gland to metabolize various xenobiotics was investigated. Adrenal microsomal and mitochondrial preparations showed a maximal absorption at 450 nm for dithionite-reduced cytochromes in the presence of carbon monoxide. Occasionally, absorption maxima at 448 nm were observed with both microsomal and mitochondrial preparations. Microsomal and mitochondrial cytochrome P-450 (448) concentrations were found to be 0.34 and 0.23 nmol/mg protein, respectively. In spite of the high microsomal cytochrome P-450 levels neither the hydrocarbons, benz[a]pyrene (BP) and 7,12-dimethylbenz[a]anthracene (DMBA), nor a variety of other substrates were metabolized to any measurable extent. In contrast, microsomal epoxide hydrolase and soluble glutathione transferase activities were high. The results may explain the low incidence of adrenal cancer in man.