Effects of surfactant protein-A on surfactant function in preterm ventilated rabbits.

Surfactant protein-A (SP-A) isolated from cow surfactant was added to organic solvent extracts of natural bovine surfactant or of Survanta (Abbott Laboratories), and dynamic compliances and pressure-volume curves were measured in rabbits with a gestational age of 27 days. Organic solvent extracts of natural surfactant and Survanta significantly improved dynamic compliances and lung volumes compared with those in control rabbits, but the effects were less than for natural surfactant. Adding 1 to 10% by weight SP-A to organic solvent extracts of natural surfactant increased dynamic compliances and maximal lung volumes on pressure-volume curves to values comparable with natural surfactant. Lung volumes at 10 cm H2O on deflation curves increased in a dose-dependent fashion at concentrations of SP-A between 0.5 and 5% by weight with no further improvement at 10% SP-A, although the volumes were significantly lower than for natural surfactant. Five percent by weight SP-A did not improve any measurements for Survanta. These results indicated that SP-A favorably improved organic solvent extracted natural surfactant function in vivo. However, the responses could not be generalized to another surfactant.