ABSENCE OF AN ADDITIONAL FIBROTIC RESPONSE CAUSED BY OXYGEN IN THE LUNGS OF RATS AFTER THE INTRATRACHEAL ADMINISTRATION OF BLEOMYCIN

Bleomycin 0.4, 0.6, 1.0 or 3.5mg/kg body weight was administered via the trachea in rats. After various time intervals some of the animals were exposed to 50% oxygen for either 4 or 24 h. The rats were then sacrificed at different times. Control rats remained untreated or received physiological saline. Lung histology was studied by light microscopy. In a number of rats the lung content of hydroxyproline was determined. Mild reactions, namely increases in pneumocytes type II and macrophages, oedema and prefibrotic alterations were observed after the instillation of bleomycin. The reactions were comparable to those observed after additional hyperoxia alone. Lung hydroxyproline concentration was not increased after bleomycin plus oxygen as compared with bleomycin alone. We conclude that no added toxicity is caused by 50% oxygen supplied for 4 or 24 h subsequent to doses of bleomycin that lead to mild pulmonary abnormalities in the absence of hyperoxia.