Cytochrome P-450 content and mixed-function oxidation by microsomes from rabbit alveolar macrophages

Cytochrome P-450 content and p-nitroanisole demethylation (a mixed-function oxidation) were investigated in the microsomal fraction from rabbit alveolar macrophages. The content of cytochrome P-450 was 0.13 +/- 0.024 (mean +/- S.E., n = 9) nmol/mg protein and was not stimulated by pretreatment of rabbits with chlorpromazine. Pretreatment with BCG resulted in decreased cytochrome P-450-specific content, suggesting that the microsomal protein pool was diluted by de novo synthesis of noncytochrome proteins. Demethylation of p-nitroanisole by alveolar macrophage microsomes during a 1 hr incubation was 17.1 +/- 1.4 nmol X hr-1 X mg protein-1. The microsomal fraction from homogenates of whole lungs had a cytochrome P-450 content of 0.32 +/- 0.078 nmol/mg protein and p-nitroanisole demethylase activity of 26.6 +/- 8.7 nmol X hr-1 X mg protein-1. The results indicate the presence of cytochrome P-450 in rabbit alveolar macrophages and show that the microsomal fraction can catalyze a mixed-function oxidation reaction. Comparison of alveolar macrophage and whole lung microsomal preparations indicates that alveolar macrophage cytochrome P-450 comprises a minor fraction of the total pulmonary pool.