Changes in pulmonary connective tissue proteins after a single intratracheal instillation of cadmium chloride in the rat.

Changes of soluble and insoluble fractions of pulmonary connective tissue proteins were studied in rats for 2-84 days following a single intratracheal instillation of cadmium chloride (10 micrograms Cd2+/lung). A transient decrease in body weight and an immediate increase in lung wet weight (200% of control value, P less than 0.01) were observed. Incorporation of [14C]proline and its conversion to [14C]hydroxyproline in vivo into different soluble and insoluble fractions of connective tissue revealed an increased metabolic turnover elicited by cadmium intoxication. A lag in the maturation of collagen into higher functional forms in the early phase of the process was demonstrated. A striking decrease in elastin was found in first 7 days (40-50%). However, this acute damage of pulmonary connective tissue was followed by a permanent increase of collagen and elastin concentration in the later phase of recovery. Histopathologic examination 14-84 days after cadmium instillation confirmed the presence of lesions in pulmonary tissue with an initial inflammation followed by reparatory changes.