FAILURE OF MECHANICAL-PROPERTIES TO PARALLEL CHANGES IN LUNG CONNECTIVE-TISSUE COMPOSITION IN BLEOMYCIN-INDUCED PULMONARY FIBROSIS IN HAMSTERS

Lung volumes and volume-pressure (V-P) relationships were measured in anesthetized hamsters 8, 30, 60 and 90 days after interstitial pulmonary fibrosis induction by intratracheal bleomycin administration. Subsequently, total collagen, elastin, protein, DNA and dry weight were determined in the lungs of each animal. The mean volume of air in the lungs at a transpulmonary pressure of 25 cm H2O and mean quasi-static compliance were decreased at 8 and 30 days and had returned toward normal by 60 and 90 days. Dry lung weight and total protein content were increased at 8 days, peaked at 30 days and were still greater than normal at 90 days. DNA peaked at 8 days, remained unchanged through day 60 and returned to normal by day 90. Collagen and elastin content, although not significantly different from control at day 8, was increased at day 30 with peak values attained at day 60 and with little decrease at day 90. Ratios of collagen or elastin to dry weight, total protein and DNA were decreased at 8 days, normal at 30 days and increased at 90 days. The ratios of collagen or elastin to total protein, dry lung weight or DNA are not indicators of the amounts of these proteins in the whole lung. In interstitial pulmonary fibrosis induced with bleomycin the pattern of changing lung biochemical composition cannot be inferred from lung volumes or V-P relations.