Effects of increasing hrDMBT1 (A) and calcium (B) concentrations on surface activity of surfactant preparations. (A) Surface activity (assessed as openness of a capillary) decreased with increasing human recombinant DMBT1 concentrations (final concentrations: 0 – 330 μg/ml) in both surfactant preparations (final phospholipid concentration 1 mg/ml). 2-way-ANOVA showed a significant influence on surface tension for surfactant preparation (P = 0.0243) and for hrDMBT1 concentration (P < 0.0001) as well as an interaction between surfactant preparation and hrDMBT1 concentration (P = 0.0363). (B) Calcium chloride antagonized the decrease of surface activity in the surfactant preparations (final phospholipid concentration 1 mg/ml) induced by hrDMBT1 (final concentration: 200 μg/ml). Analysis of variance analysis stated an influence of surfactant preparation (P = 0.0004), of hrDMBT concentration (P < 0.0001) and an interaction between surfactant preparation and hrDMBT1 concentration (P = 0.0037). Note that the surface activity of Alveofact® decreased at a lower hrDMBT1 concentration than that of Curosurf® (A) and that calcium antagonized the hrDMBT1 effect at 1 mM, whereas Alveofact® required a calcium concentration >3 mM (B). Data are expressed as mean ± SEM.