Lung growth after unilateral pneumonectomy: quantitation of collagen synthesis and content

Unilateral pneumonectomy in the adult rabbit causes the mass of the remaining lung to double within 1 mth. The content and synthesis of lung collagen were compared in 113 rabbits with pneumonectomy, thoracotomy without pneumonectomy, or pneumonectomy with subsequent wax plombage. By the 28th day after left pneumonectomy, total lung collagen and cell number were nearly 100% greater than matched control values, but the density of both collagen and cell number remained constant and unchanged from control. This collagen accumulation was preceded by an increase in the rate of collagen synthesis per cell and in the percent of lung total protein synthesis represented by collagen synthesis. In normal neonatal lung growth, total lung mass, collagen, and cell number increase. During this same period there is also an increase in the % of collagen synthesis represented by lung total protein synthesis; however, in contrast to postpneumonectomy adult lung growth, the density of collagen increases. Obliteration of the empty hemithorax with wax after pneumonectomy resulted in suppression of the increases in right lung cell number, collagen synthesis, and collagen accumulation seen with pneumonectomy alone. This could have generalized implications relating to the control of lung gene expression in that lung cell replication and/or lung cell differentiation may, in part, be controlled by the available space into which the lung may grow.