Administration of exogenous surfactant to affected newborns promotes clearance of extravascular lung water. Although changes in pulmonary compliance contribute to clearance of alveolar salt and water, the possibility of a direct effect remains. To test the hypothesis that exogenous surfactants incorporate channel activity into plasma membrane, Survanta® (SUR) and Exosurf® (EXO) were probed for channel activity in the planar lipid bilayer model. Methods: Artificial lipid bilayers (3:1 phosphatidylethanolamine: phospha-tidylserine) were painted across an aperture connecting compartments of buffered (pH 7.0) salt solutions. Gradients (150:50 mM) of Na+ gluconate were established across bilayers. SUR or EXO was added to the hypertonic compartment. Holding potentials were applied across bilayers, currents measured, and slope conductance (gs) calculated. Results: Untreated bilayers exhibited no electrical activity. SUR (0.03%) induced current flow characterized by: 1) channel gating between open and closed states; 2) voltage-dependent open state probability; 3) cationic gs = 86 pS; 4) transport turnover of≈5×107 ions/sec; 5) Na+ dependence (choline+ buffer eliminates current flow); 6) anion independence; and 7) inhibition by Na+ channel blocker, amiloride (1 mM). By contrast, EXO did not induce current flow. Conclusions: SUR - but not EXO - induces channel-mediated (as opposed to simple diffusion or carrier-mediated) transport of Na+ in artificial lipid bilayers as demonstrated by observed channel gating, high transport turnover rate and amiloride inhibition. We speculate that SP-B or SP-C contributes to channel formation through promotion of liposome fusion with bilayers or through insertion of channel structures. (Funded by Children's Health Foundation)
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Oelberg, D., Raiko, A. & Bartschat, D. EXOGENOUS SURFACTANT PREPARATION INITIATES SINGLE CHANNEL CURRENT FLOW IN ARTIFICAL LIPID BILAYERS. † 2047. Pediatr Res 39 (Suppl 4), 344 (1996). https://doi.org/10.1203/00006450-199604001-02071
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DOI: https://doi.org/10.1203/00006450-199604001-02071