SURFACE-PROPERTIES AFTER A SIMULATED PLA(2) HYDROLYSIS OF PULMONARY SURFACTANTS MAIN COMPONENT, DPPC

The inflammation, so conspicuous in cases of respiratory distress. pne umonia, and asthma, is associated with an airway invasion of plasma pr oteins and a release into the airway lumen of phospholipase A, (PLA,), This enzyme catalyzes hydrolysis of surfactant phospholipids, the mos t abundant and important of which is dipalmitoylphosphatidylcholine (D PPC). Its hydrolysis yields equimolar proportions of lysophosphatidylc holine and palmitic acid (LPC/PA), Exact quantification of DPPC hydrol ysis is complicated. Consequently. it was decided to simulate hydrolys is whereby DPPC (3 mg/ml) was gradually replaced with LPC/PA (3 mg/ml) , yielding seven different grades of simulated hydrolysis: 0, 17, 33, 50, 67, 83, and 100%. Surface properties of the seven mixtures were ex amined with various concentrations of albumin added. The Bubble Surfac tometer was used to study the surfactant film that is given time to de velop at a spherical air-liquid interface. A Capillary Surfactometer w as used to evaluate surface properties required for airway patency. It was found, using both of these instruments that the surface activity improved as the simulated hydrolysis of DPPC to LPC/PA increased towar d 100%, where the activity was maximal. With the Bubble Surfactometer, surface activity of LPC/PA, 3 mg/ml, improved as albumin concentratio n increased, and when it reached 15 mg/ml, surface tension became 0 mN /m after only 2 min. With the Capillary Surfactometer, requiring a muc h faster film adsorption, albumin had an opposite effect. LPC/PA alone maintained patency 100% of the time studied, while even a minimal add ition of albumin inhibited surfactant function. (C) 1997 Elsevier Scie nce B.V.