An effect of corticosteroids and 100% oxygen on aryl hydrocarbon hydroxylase, cytochrome-c reductase, and free radical formation by rat lung microsomes.

Activity of aryl hydrocarbon hydroxylase (AHH), cytochrome c-reductase, and NADPH oxidase, and epinephrine oxidation to adrenochrome were determined in lung microsomes from intact, adrenalectomized, and adrenalectomized cortisol-treated female rats under ambient and hyperoxic conditions. Microsomal adrenochrome formation, which is initiated by superoxide anion or other free radicals, was increased by adrenalectomy and decreased by cortisol treatment. Exposure of animals to 100% oxygen caused a further increase in adrenochrome formation. NADPH-cytochrome c-reductase and AHH activities were increased in incubations of microsomes from animals which had received cortisol in vivo while adrenalectomy led to decreases activity. NADPH oxidase activity was increased by cortisol in lung microsomes in the presence of either epinephrine or cytochrome c. Epinephrine conversion to adrenochrome in the presence of lung microsomes was blocked by SOD, but NADPH-cytrochrome c-reductase and AHH activity were unaffected.