[Participation of pulmonary macrophages in regulating the quantity of surfactant on the alveolar surface]

The fixation of the rat lung by perfusion through the pulmonary artery permits to prevent the "washing out" of macrophages into the alveolar lumen and to preserve their natural disposition in the hypophase of the alveolar lining layer beneath the surfactant film. The surfactant synthesis was enhanced in the granular alveolar cells (type II) of the remaining lung 5 to 7 days after the leftside pneumonectomy; the amount of the tubular myelin in the hypophase of the hypertrophic alveoli increased, and the surface tension of the lung washings diminished. At that period the alveolar macrophage count more than doubled. The alveolar macrophages utilized the excess of surfactant (the tubular myelin) in the hypertrophic lungs, thereby taking part in the regulation of the alveolar surface tension.