Pulmonary toxicity of cadmium in rats: a histologic and ultrasound study

Several studies have shown a carcinogenic effect of inhaled or injected cadmium in rats. This carcinogenity has not yet been confirmed in humans. We have performed a study with 48 Wistar male rats, to which we have administered either cadmium sulphide (0.2 mg/Kg/day) or the same doses of placebo for four or eight days. 24 hours after the last administration, the rats were euthanised and an autopsy was performed. The histologic changes in the lung of the cadmium-exposed group were diffuse areas of alveolar collapse due to narrowing of the bronchioles secondary to the alteration of the surrounding connective tissue, with compensating alveolar emphysema near these foci and also at the periphery of the lung. There was also an increased number of intra-alveolar macrophages. We also noticed small foci of dysplasia in the alveolar epithelium. Ultrastructural changes were inspecific but suggested a toxic effect of cadmium on the epithelium. These findings, absent in the control group, confirm that intrathoracic injection of cadmium is associated with an increased tendency to the development of pulmonary emphysema and with dysplastic changes in the alveolar epithelium (peribronchiolar alveolar dysplasia).