Comparison of three lipid formulations for synthetic surfactant with a surfactant protein B analog

Surfactant protein B (SP-B) is an essential component of pulmonary surfactant. Synthetic dimeric SP-B_1-25 (SP-B_1-25), a peptide based on the N-terminal domain of human SP-B, efficiently mimics the functional properties of SP-B. The authors investigated the optimum lipid composition for SP-B_1-25 by comparing the effects of natural lung lavage lipids (NLL), a synthetic equivalent of NLL (synthetic lavage lipids SLL), and a standard lipid mixture (TL) on the activities of SP-B _1-25. Surfactant preparations were formulated by mixing 2 mol% SP-B_1-25 in NNL, SLL, and TL. Calfactant, a calf lung lavage extract with SP-B and SP-C, was a positive control and lipids without peptide were negative controls. Minimum surface tension measured on a captive bubble surfactometer was similar for the three SP-B_1-25 surfactant preparations and calfactant. The effects on lung function were compared in ventilated, lavaged, surfactant-deficient rats. Oxygenation and lung volumes were consistently higher in rats treated with calfactant and SP-B_1-25 in NLL or SLL than in rats treated with SP-B_1-25 in TL. Fourier transform infrared spectra observed abnormal secondary conformations for SP-B_1-25 in TL as a possible cause for the reduced lung function. Lipid composition plays a crucial role in the in vitro and in vivo functions of SP-B_1-25 in surfactant preparations.