In vitro inactivation of pulmonary surfactant replacement preparations by serum albumin

Inactivation of the surface activity of pulmonary surfactant by serum proteins is an important part of neonatal respiratory distress syndrome. The ability of serum proteins to diminish the surface activity of surfactant preparations used to treat respiratory distress syndrome has not been fully described. The sensitivity of clinically useful pulmonary replacement preparations beractant (Survanta) and colfosceril palmitate, cetyl alcohol, and tyloxapol (Exosurf) to albumin inactivation was examined in vitro by the Wilhelmy plate technique. At a final lipid concentration of 0.1 mg/mL and in the absence of albumin, both Survanta and Exosurf exhibited equilibrium surface tensions in the range of 35 dynes/cm. In the presence of albumin, range of 35 dynes/cm. In the presence of albumin, the surface tension of Survanta was markedly higher. Maximal response of Survanta to albumin was observed at about 1 mg/mL protein concentration. When the lipid concentration was raised to 0.3 mg/mL, the presence of albumin had little effect. With Exosurf, the presence of albumin resulted in only minor elevations of surface tension, even at an albumin concentration 10-fold greater than that used in the experiments with Survanta. These results indicate that at lipid concentrations of 0.1 mg/mL and less, the surface activity of the bovine purified lung surfactant Survanta is more sensitive to the presence of albumin than is the synthetic preparation Exosurf.