Alterations in cell proliferation in mouse lung following urethane exposure. 3. Effects of chronic exposure on type 2 alveolar epithelial cell.

The effect of chronic urethane exposure on proliferation of Type 2 alveolar epithelium was investigated by autoradiography. Control mice and mice exposed for 10 weeks to urethane in drinking water were injected with (3)H thymidine and killed at intervals for 7 days. Mean grain counts of Type 2 alveolar cells in the 2 groups showed that the cell cycle time of test mice was prolonged when compared with an estimated 22-hour cycle for controls; this was accompanied by a fivefold increase in labeling index in test animals.