Aryl hydrocarbon hydroxylase and its components in human lung microsomes

Microsomal fractions were prepared from specimens of human tissues obtained at surgical resections of 16 patients suffering from different types of pulmonary tumors. The contents of cytochrome P-450 and the activity of aryl hydrocarbon hydroxylase in human samples were much lower than the levels in rodent lung microsomes. The content of cytochrome b5 and the activities of NADPH-cytochrome P-450 reductase and of NADH-cytochrome b5 reductase, however, corresponded to those of rodent lung microsomes, with mean values of 0.12 nmol/mg protein, 0.039 and 3.58 mumol/min/mg protein, respectively.