CYP2E1 IS PREFERENTIALLY EXPRESSED IN CLARA CELLS OF MURINE LUNG - LOCALIZATION BY IN-SITU HYBRIDIZATION AND IMMUNOHISTOCHEMICAL METHODS

The purpose of this study was to investigate the expression and distri bution of pulmonary CYP2E1 in mice. The CYP2E1 protein and mRNA were i dentified by immunoblotting and northern blotting, respectively, while the distribution of the CYP2E1 protein and mRNA was examined by immun ohistochemistry and in situ hybridization, respectively. Protein immun oblotting revealed a single band of similar to M(r) 51,000 in lung mic rosomes of CD-1 male mice. Northern blotting with a P-32-labeled RNA p robe for CYP2E1 detected a single species of similar to 2 kb that was similar in size to that of liver CYP2E1. Immunohistochemical studies w ith the avidin-biotin complex procedure showed that CYP2E1 was localiz ed prominently in the nonciliated Clara cells but was not detected in the ciliated cells of the bronchiolar epithelium. In the lung parenchy ma, immunoreactivity for CYP2E1 was evident at minimal levels in alveo lar type II cells. In situ hybridization experiments with a P-31-label ed RNA probe showed that the CYP2E1 mRNA was also predominantly locali zed in the bronchiolar epithelium and was most prominent in the Clara cells. As was found for the CYP2E1 protein, the CYP2E1 mRNA was minima l in cells of the lung parenchyma. These results demonstrated that the CYP2E1 enzyme is preferentially expressed in Clara cells of murine lu ng. The concentration of CYP2E1 mainly in this cell population may be an important determinant underlying its susceptibility to cytotoxiciti es induced by xenobiotics bioactivated by this P450 isozyme.