The subcellular distribution of NADPH-cytochrome P450 reductase and isoenzymes of cytochrome P450 in the lungs of rats and mice.

NADPH-cytochrome P450 reductase was localized by ultrastructural immunocytochemistry in the cytoplasm of Clara cells, ciliated cells and type II pneumocytes of young female Wistar rats and MF1 mice. Immunogold labelling was particularly dense over the apical cytoplasm of Clara cells. CYP1A was only detected in lungs of animals treated with Aroclor 1254 or 3-methylcholanthrene; it was localized in the cytoplasm of Clara cells of rats and in the endothelial cells of both rats and mice. In rat lung the labelling of cytochrome P450 CYP2B was most intense in the apical cytoplasm of Clara cells, but it was also found in both the type I and type II cells of the alveolar epithelium. Similar immunoreactivity was found in the Clara and type II cells of mice, it was also found in the ciliated cells of this species. CYP4B was localized in the cytoplasm of Clara and type II cells of rats. The cell-specific concentration of these isoenzymes, particularly that of CYP2B in the cytoplasm of type I cells, probably contributes to the particular susceptibility of these cells to pneumotoxins.