肺 そのユニークな構造と機能 肺サーファクタントの界面化学的性質

Abstract

Lung surfactant plays an important role of normal respiration to reduce the surface tension at the air-liquid interface of the alveoli and prevents collapse of the lung. The deficiency of lung surfactants causes respiratory distress syndrome (RDS) in premature infants. Thus, many synthetic lung surfactants for RDS treatment have so far been studied and developed by many researchers.The aerosol delivery of dipalmitoyl phosphatidyl choline (DPPC) as a principal ingredient of lung surfactant was attempted for RDS treatment, but it had no effect. On the other hand the effective synthetic lung surfactant for RDS including surfactant proteins extracted from bovine lung, named TA, has been developed by Fujiwara et al.The characteristics of synthetic lung surfactants with or without the surfactant proteins, SP-B, SP-C and SP-BC, were evaluated on the basis of surface modulus and viscosity obtained by applying the Maxwell model to the relaxation of the surface pressure produced by an area strain of 10% on a monolayer on the surface of a buffer solution and were compared with those of the synthetic lung surfactant TA developed earlier. The surface shear modulus and viscosity characteristic of the surface rheology for synthetic lung surfactant TA containing a trace of SP-BC showed a constant value for area strain of 10% under all equilibrium surface pressures and coincided with values of the mixed monolayers obtained by adding SP-BC and SP-B + C to the other components of lung surfactant (except surfactant proteins), but these moduli and viscosities for the systems without surfactant proteins increased with increase in equilibrium surface pressures. These results suggest that the existence of a trace of SP-BC in the synthetic lung surfactant TA improves its effectiveness and may serve as a 'cushion' among dipalmitoyl lecithin molecules in the monolayers during surface compression and expansion of these monolayers.