Peribronchiolar fibrosis following acute experimental lung damage by cadmium aerosol

Following exposure to an aerosol of 0.1 per cent. (0.005M) cadmium chloride in physiologic saline, rat lungs were examined at 1 hour, 1, 2, 3, 4, 5, 7, 10 and 21 days. Light microscopy showed that damage was most marked about respiratory bronchioles with a prominent increase in interstitial cells. Up to 3 days the intestitial cells were closely packed and monocytic in type, but on the fourth and fifth days, the cellular density had decreased and elongated cells resembling fibroblasts appeared. By 7 days the interstitial cells were predominantly fibroblastic. Ultrastructurally the fibroblasts were active with prominent rough endoplasmic reticulum and numerous, single, haphazardly scattered collagen fibrils in lacunae at the cell margins. At 21 days after injury, interstitial collagen was seen as well organised, mature bundles. The fibrosis was seen in a peribronchiolar position with distoration of the bronchiole and adjacent alveoli. We suggest that the peribronchiolar localisation of fibrosis is the probable cause of centriacinar emphysema resulting from acute cadmium fume poisoning in man.