Lung tissue elasticity during the lifespan of Fischer 344 rats

Fischer 344 rats at 1 week, 6 weeks, 5 months, 14 months, and 22 months of age were studied. Lung wet and dry weights and lung volumes increased with age. As rats grew older, saline volume-pressure (V-P) curves expressed as percent maximal lung volume shifted progressively upward and to the left and tissue recoil decreased over the upper and mid portions of the V-P relationships. Specific lung compliance increased until 5 months of age but did not change afterward. DNA content of the lung increased progressively until 5 months of age but decreased in older rats. Protein content of the lung increased significantly with age, while hydroxyproline and crude connective tissue content of the lung increased progressively until 14 months of age. Decreased tissue recoil and increased lung volume and lung compliance with age, in face of an increase in connective tissue proteins, suggest that larger air space dimensions might be responsible for changes in lung mechanics in aging rats.