Function and inhibition sensitivity of the N-terminal segment of surfactant protein B (SP-B1-25) in preterm rabbits.

BACKGROUND Surfactant protein B (SP-B) is an essential component of pulmonary surfactant, but shorter SP-B sequences may exert equivalent surface activity. METHODS We synthesised a peptide based on the amino-terminal domain of SP-B (SP-B1-25), a full length SP-B1-78, and a full length palmitoylated SP-C peptide (SP-C1-35) and compared the in vivo function and sensitivity to plasma inhibition of preparations consisting of mixtures of phospholipids with SP-B1-25 or SP-B1-78 and/or SP-C1-35 to Survanta. Preterm rabbits born at 27 days of gestation were treated at birth with surfactant and ventilated for 60 minutes. At 15 minutes half of them received plasma intratracheally. Dynamic compliance was monitored every 15 minutes and postmortem pressure-volume curves were measured to define lung mechanics. RESULTS Dynamic compliance and postmortem lung volumes were highest after treatment with a surfactant consisting of an SP-B peptide and SP-C1-35 or Survanta. Plasma instillation decreased dynamic compliance and lung volumes sharply, but the most effective activity was by prior instillation of surfactants containing SP-B1-25. CONCLUSION These experiments suggest that the N-terminal domain of SP-B (SP-B1-25) exhibits in vitro and in vivo surface activity and is relatively insensitive to plasma inhibition.