Reduction in rabbit serum and pulmonary angiotensin converting enzyme activity after subacute bleomycin treatment

We studied morphological and biochemical alterations in the lungs of rabbits treated subcutaneously with bleomycin (5 mg/kg) three times weekly for 28 days. This treatment produced morphologically evident pulmonary damage characterized by the appearance of ciliated alveolar epithelial cells and endothelial blebs. No change in pulmonary collagen content was evident. Rabbits treated with bleomycin had significantly less pulmonary angiotensin converting enzyme activity than control animals, although no alterations in lung DNA, protein, glycosaminoglycans or hydroxyproline (an index of collagen) were observed. Serum angiotensin converting enzyme activity decreased with repeated bleomycin administration and was reduced by 42, 48 and 65 per cent from control animals 2, 3 and 4 weeks, respectively, after the initiation of drug treatment. These data provide biochemical evidence that subacute bleomycin administration damages the pulmonary endothelium in the absence of fibrosis and can reduce the serum activity of angiotensin converting enzyme in rabbits.