Effect of ventilation on surfactant, and its turnover rate.

Abstract

Air pressure-volume [P-V] curves were performed on excised rat and dog lungs. In rats, P-V curves were performed before and after tracheal lavage with nonionic detergent of varying concentrations, after ventilation at various rates and temperatures, and after exposure to cyanide by right ventricular injection. Surface activity of postventilated lungs was assayed. The effect of cyanide on surfactant and dipalmitoyl lecithin was studied. The pressure-volume characteristics were consistent, and comparable to other mammals. Nonionic detergent altered compliance secondary to alteration of surface forces. Greater than tidal volume ventilation rapidly caused decreased distensibility in rat lungs; the change was greater at higher ventilatory rates. Incubation at 37 C could completely reverse the ventilation effect. Ventilation at 37 C did not cause a decrease in compliance. Cyanide and cold deterred recovery after ventilation. Cyanide decreased the surface activity of surfactant, but did not affect dipalmitoyl lecithin. Surfactant is rapidly modified by ventilation, especially at high rates; it is replaced by processes involving cellular metabolism. Alteration of the protein can modify the surface activity of surfactant.