Compensatory pulmonary hypertrophy after incapacitation of one lung in the rat

Following removal of the rat's right lung, which averages twice the weight of the left one, the remaining pulmonary tissue doubles in relative weight after 4 wk. In an attempt to determine which physiologic deficits are responsible for triggering contralateral compensatory hypertrophy, following unilateral pneumonectomy (UP), right lungs were incapacitated in various ways, with the following results. Bronchial occlusion (BO) elicited as much compensatory hypertrophy as did unilateral pneumonectomy. Pulmonary arterial ligation (PAL) caused growth of the opposite lung to 48% over control values. Atelectasis (A), achieved by injecting silicone rubber into the right pleural cavity, allowed only a 26% increase in relative weight of the left lung. The degrees of compensatory pulmonary hypertrophy obtained in these experiments are roughly proportional to the expected extents to which the function of the opposite lung has been interrupted, namely, UP = BO > PAL > A.