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 pulmona ry surfactant, but shorter SP-B sequences may exert equivalent surface acti vity. 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 p eptide (SP-C1-35) and compared the in vivo function and sensitivity to plas ma 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 2 7 days of gestation were treated at birth with surfactant and ventilated fo r 60 minutes. At 15 minutes half of them received plasma intratracheally. D ynamic compliance was monitored every 15 minutes and postmortem pressure-vo lume curves were measured to define lung mechanics. Results-Dynamic compliance and postmortem lung volumes were highest after t reatment with a surfactant consisting of an SP-B peptide and SP-C1-35 or Su rvanta. Plasma instillation decreased dynamic compliance and lung volumes s harply, but the most effective activity was by prior instillation of surfac tants 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 in sensitive to plasma inhibition.