Metabolism of 2-acetylaminofluorene by Clara cells, type II cells and alveolar macrophages isolated from rabbit lung, and use of a new chamber incubation mutagenicity test system.

Clara cells, alveolar type II cells and pulmonary alveolar macrophages (PAM) were isolated in high yield from rabbit lung. The purity of the cell fractions was 80-90%, 98% and above 99%, respectively. Cytochrome P-450 total content was determined in microsomes from freshly prepared cells. The Clara cells contained significantly more cytochrome P-450 than was found in whole lung microsomes. Furthermore, the cytochrome content of the Clara cells was 2-fold higher than in the type II cells and 4-fold higher than in the macrophages. 2-aminofluorene (AF) was the major metabolite in all preparations when intact cells were incubated with 2-acetylaminofluorene (AAF). The PAMs produced AF in the highest rates, while the Clara cells showed the largest rates of cytochrome P-450-dependent, ring hydroxylation of AAF. Mutagenic activation of AAF by isolated lung cells was assayed with a chamber-incubation method. The Clara cells were far more active than the type II cells in this respect, while the macrophages were inactive.