RADIOIMMUNOASSAY OF PULMONARY SURFACE-ACTIVE MATERIAL IN TRACHEAL FLUID OF FETAL LAMB

Abstract

The pulmonary surfactant antigen was measured by radioimmunoassay and phospholipid by lipid phosphorus assay in fluid collected during 12 h periods from the trachea of lambs in utero 102-147 days of gestation. Both phospholipid and antigenic protein were detectable at 114 days and were present at low concentrations until 137 days. The concentrations then increased rapidly and reached 5 to 10-fold higher concentrations before parturition. The ratio of lipid phosphorus to antigen increased approximately 5-fold as the lungs passed from canalicular to alveolar architecture and approximated the adult ratio only during the alveolar stage of development.