Effects of Serum Proteins on Pulmonary Surfactants In Vitro

Evidence of a Protective Mechanism In Pulmonary Edema

¹ Cardiothoracic Institute associated with the London Chest Hospital, London, England

Using a new photographic modification of Pattle and Burgess'¹ bubble method for measuring surface tension of fluids, evidence is presented here to suggest for the first time that plasma proteins may assist pulmonary surfactants in lowering surface tension in alveoli that are the site of pulmonary edema. The present experiments show that the stability of small air bubbles in solutions of phospholipids is increased by adding human albumin or globulin. Similarly, the stability of small bubbles in fluid expressed from surgical specimens of human lungs is increased by adding human plasma.

On the basis of these findings, it is suggested that the surfactant system should be regarded as a constantly varying protein-lipid system and that the efficiency of this system may be increased by adding serum protein, a protein-adding effect, or lipid, a lipid adding effect. There is no evidence to support the widely held belief that plasma proteins inhibit surfactants.