Cytoplasmic activity in type I pulmonary epithelial cells induced by macroaggregated albumin

After the intravenous injection of radioalbumin macroaggregate, large numbers of cytoplasmic inclusion bodies were observed in the lung tissue of rats. The inclusions were located mainly in the cytoplasm of type I alveolar lining cells, appeared 40 minutes after the injection, and lasted up to 2 days. These observations suggest that the type I alveolar lining cells participate in the clearing mechanism of the lung tissue, a function that thus far has not been attributed to this type of cell.