Acute lung injury induced by cadmium aerosol. I. Evolution of alveolar cell damage

Following exposure to an aerosol of 0.1% (.005 M) cadmium chloride, rat lungs were examined at 6 hours and 1, 2, 3, 4, 7, and 10 days. By light microscopy, damage was multifocal and centered about respiratory bronchioles. Ultrastructurally, there was Type 1 cell edema with frequent loss of surface plasma membranes during the first 24 hours. After 2 days, the number of Type 2 cells had markedly increased, and by 3 days the damaged alveoli were lined by plump cuboidal cells closely resembling Type 2 cells. By 4 days, these cells were flatter, the change being more marked by 7 days; by 10 days, the cells had regained the appearance of Type 1 cells through loss of osmiophilic bodies and superficial microvilli. We conclude that CdCl2 damages Type 1 cells, which are then replaced by proliferation of Type 2 cells. These cells lose their osmiophilic bodies and flatten out to replace the lost Type 1 cells, the process being almost complete by 10 days after the injury. This pattern resembles the injury caused by NO2, O3, and O2.