In vivo function of surfactants containing phosphatidylcholine analogs.

Increased phospholipase A2 activity demonstrated in some forms of lung injury may contribute to surfactant dysfunction. Phospholipase A2-resistant analogs of dipalmitoylphosphatidylcholine (DPPC) with surfactant properties might therefore be useful lipid components of treatment surfactants for certain lung injuries. The in vivo function of surfactants containing DPPC or the phospholipase-resistant analogs dihexadecylphosphatidylcholine (DEPC) or dihexadecylphosphonotidylcholine (DEPnC), with or without surfactant proteins B and C (SP-B+C), was thus evaluated in preterm rabbits (27 days' gestation). Rabbits randomly received one of seven surfactants (DPPC, DEPC, DEPnC, DPPC+SP-B+C, DEPC+SP-B+C, DEPnC+SP-B+C, or lipid extract surfactant [LES]) or 0.45% NaCl (control) and were ventilated for 30 min. Lipid-only surfactants decreased ventilatory pressures (peak inspiratory pressures minus positive end-expiratory pressure) relative to control (p < 0.05). Addition of SP-B+C further decreased ventilatory pressures to levels similar to LES (p < 0.01 versus control, lipid-only surfactants). Lung dynamic compliances and postventilation pressure-volume curves improved in the following order: LES, SP-B+C lipid surfactants > lipid-only surfactants > control (p < 0.05). All surfactant preparations decreased intravascular 125I-albumin recoveries in the lungs relative to control (p < 0.01 for all surfactants versus control). These results indicate that DEPC and DEPnC were as effective as DPPC as lipid components of synthetic surfactants. And like DPPC, the analogs interacted with isolated SP-B+C and improved in vivo function to levels comparable to LES.