ACTIVE SURFACTANT IN PHARYNGEAL ASPIRATES OF TERM NEONATES - LIPID BIOCHEMISTRY AND SURFACE-TENSION FUNCTION

Alveolar surfactant is well known for its ability to reduce minimal su rface tension at the alveolar air-liquid interface to values below 5 m N m(-1). In addition, it has been suggested that surfactant is also pr esent in the airways, particularly in the perinatal period. We isolate d surfactant from pharyngeal aspirates obtained from 33 neonates immed iately after delivery and analysed it for both phospholipid (PL) compo sition and surface tension function. PL classes and phosphatidylcholin e (PC) molecular species were determined by normal and reversed-phase high-performance liquid chromatography (HPLC), respectively. Static an d dynamic surface properties of the surfactant were studied in a pulsa ting bubble surfactometer. Sample volume was 1.3 +/- 0.5mL (mean +/- S D) with a total amount of 2.5 +/- 1.3 mu mol of PL and a concentration of 2.1 +/- 1.0 mu mol mL(-1) FL. HPLC analyses of PL classes revealed a composition identical with surfactant prepared from alveolar washes , i.e. PC 83.6 +/- 2.1%, sphingomyelin 1.4 +/- 0.5%, phosphatidylglyce rol 8.1 +/- 1.6%, phosphatidylethanolamine 2.1 +/- 0.5% and phosphatid ylinositol 2.6 +/- 1.1%. Thin-layer chromatography showed almost ident ical results but was more time-consuming and needed more material for analysis. Analysis of PC molecular species revealed a composition typi cal of human alveolar surfactant with 54.7 +/- 3.9% dipalmitoyl PC, 10 .3 +/- 1.9% palmitoyloleoyl PC and 9.1 +/- 1.5% palmitoylmyristoyl PC. Minimal surface tension fell to values below 5 mN m(-1) within 5 min of cycling in all subjects, The methods used in this study allowed for complete PL and surface tension analyses of surfactant obtained durin g routine pharyngeal suctioning after delivery at term. Whether they a re also applicable to preterm neonates with respiratory distress remai ns to be determined.