Collagen accumulation in the major structures of the rabbit lung during postnatal development

In order to study the accumulation of collagen during postnatal development in the major structures of the lung, trachea, bronchi, pulmonary vasculature, and parenchyma were isolated from the lungs of 1-week, 2-month, and 6-month-old rabbits. The concentrations of DNA, protein, and collagen in parenchyma were similar to those for whole lung. DNA per day weight for all structures declined with age. The DNA concentration of trachea at 6 months was only one-tenth that of parenchyma. Protein per dry weight was constant in parenchyma but dropped by half in trachea and nearly that in bronchi. Collagen per dry weight increased significantly between 1 week and 6 months in all structures. The collagen concentrations in vessels, bronchi, and trachea are similar to each other and three to five times that of parenchyma. The total amount of collagen in bronchi, trachea and parenchyma increased approximately 12-, 50-, and 90-fold, respectively, between 1 week and 6 months of age.