PHOSPHATIDIC ACID PHOSPHOHYDROLASE AND PHOSPHOLIPIDS IN TRACHEAL AND AMNIOTIC FLUIDS DURING NORMAL OVINE PREGNANCY

Abstract

Summary: Samples of amniotic fluid and fetal tracheal fluid were obtained from 36 ovine mancies which were studied either acutely or chronically during the last two-thirds of ation (65 to 149 days). The specific activity of phosphatidic acid phosphohydrolase (Pase), disaturated lecithin (DSL), total phospholipids (TPL), and the L/S ratio were Eyed in the amniotic and tracheal fluids. There was a significant and progressive ease in the specific activity of PAPase in trache3 fluid beginniqaher 110 days, easing from 66 t 7 nmoles phosphate released x mg-1 protein x hour-1 (Mean ± S.E.M.) I days, to 107 ± 6 at 111 to 120 days, and to 277 ± 70 at 131 to 144 days. The rise in case specific activity was followed by a parallel rise in the DSL fraction of the TPL DS-L/TPL ratio), increasing from a DSL/TPL ratio of 0.06 ± 0.01 in fetuses ≤ 120 days, 0.29 ± 0.06 at 121 to 130 days, and to 0.50 ± 0.18 at 131 ± 135 days. The PAPase specific activity and the L/S ratio in amniotic fluid did not change during pregnancy. Speculation: Neonatal respiratory distress syndrome is the result of inadequate production of race active material by the fetal and neonatal lung. The enzyme PAPase occupies a tral role in the biosynthesis of the glycerophospholipids, and increases in the specificity of PAPase in human amniotic fluid and in fetal rabbit lung tissue precede or are parallel with the increase in the L/S ratio and pulmonary surfactant synthesis, reactively. We have shown that this sequence is also demonstrable in ovine fetal heal fluid, thus providing an animal preparation in which the formation and speculation of surfactant biosynthesis during fetal lung maturation can be investigated in vivo.