The effect of different concentratlons of surfactant-associated proteln C on the surface tension reducing activity of reconstituted surfactant / 中华麻醉学杂志

ABSTRACT

Objective The reconstituted pulmonary surfactant (SP) is composed of synthetic lipid(SL) and surfactant- associated protein C (SP-C) . The purpose of this study was to determine the surface tension reducing activity of the reconstituted surfactant containing different concentrations of SP-C.Methods Pulmonary surfactant (SP) was isolated from alveolar lavage fluid of fresh porcine lungs by centrifugation, extraction and precipitateon. SP-C was extracted from PS and SL was prepared by mixing dipalmitoyl-phosphatidyl choline (DPPC), dioleoyl-phosphatidyl choline (DOPC) and palmitoyl-oleoyl-phosphatidyl glycerol (POPG) in the weight ratio of 60 20 20. Three synthetically reconstituted surfactants RS-1, RS-2, RS-3, were prepared by adding different concentrations of SP-C to SL. The end concentration of SP-C was 1% , 2% and 3% respectively. Five test liquids (PS, SL. RS-1, RS-2, RS-3) were prepared by suspending the materials mentioned above in nonnal saline. The dynamic surface tension of the five test liquids were measured by a pulsating bubble technique. Thirty-six PS-deficient premature rabbits were studied. The premature rabbits were delivered by cesarean section on the 26 th day of pregnancy. The animals were tracheostomized and mechanically ventilated. 0.1 ml of test liquid PS (group Ⅱ) , SL(group Ⅲ) or RS-3(group Ⅳ) was instilled into the lungs via the tracheostomy cannula. In control group (group Ⅰ) no test liquid was instill. The animals were placed in a body plethysmograph and mechanically ventilated (the maximum inspiratory pressure = 25 cm H2 O, RR = 40 bpm, I E = 11, FiO2 = 100 % made of ventilation IPPV) . Tidal volume was measured at 5, 10, 15 and 20 min after onset of IPPV. Results The minimum surface tension (?min) of PS was 0.9?0.3 mN?m-1 , and of SL was 22.6 ?1.3 mN?m-1 . The ? min of RS-3 was 0.7?0.1 mN ?m-1. The mean tidal volume after 20 min of mechanical ventilation in group Ⅱ(PS) and groupⅢ(RS-3 ) was 25 ?7 ml?kg-1 and 25 ? 4 ml?kg-1 respectively, significantly larger than that in control group (Ⅰ ) and group Ⅲ (SL) . Conclusion The surface tension-reducing activity of SL alone is low. Adding SP-C to SL greatly enhances the surface tension-reducing activity of reconstituted surfactant (RS).