Fetal Lung Maturation

Abstract

The presence of phosphatidic acid phosphohydrolase (PAPase) in human amniotic fluid is demonstrated. The identity of the enzyme was established by the demonstration that the activity of the amniotic fluid enzyme was markedly decreased by the addition of known inhibitors of the enzyme and the pH optimum. The specific activity of PAPase in amniotic fluid increases from 15 nmol of phosphate release per milligram protein per hour at 20–32 weeks of gestation to 82 nmol in pregnancies of 35 weeks gestation and beyond (p < 0.001).

Phosphatidic Acid Phosphohydrolase and Phospholipids in Tracheal and Amniotic Fluids During Normal Ovine Pregnancy

“…Previously we observed that the specific activity of PAPase in fetal rabbit lung tissue and in human amniotic fluid increased a t or before the time of augmented surfactant synthesis (10,12,22). These findings were suggestive that the metabolism of phosphatidic acid occupies a central position in de nova pathways of phopholipid biosynthesis in Lung tissue as well a s other tissues T 2 5 ) 1 also was found that the specific activity of PAPase in the gastric aspirate or nasopharyngeal secretions of neonates a t birth was greater than that in samples of arnniotic fluid obtained from the same infants, a finding that provided strong evidence that the fetal tracheal fluid, i.e.…”

“…Rosenfeld, CR, Worley, RJ, Milewich, L, Gant, NP, Jr., and Parker, CR, nasopharyngeal fluid and amniotic fluid in the human (12) is a remarkable surge in the concentration of DS-L, expressed as t h e DSLITPL ratio, that followed closely and was parallel with the rise in PAPase activity (Figure 4). This surge in the DS-LITPL ratio in fetal tracheal fluid occurred at the same time in pregnancy as the previously reported increases in surfactant activity in ovine fetal tracheal fluid and lung tissue homogenate when expressed as either disaturated lecithin concentration (6,23), surfactant flux (16).…”

“…These findings were suggestive that the metabolism of phosphatidic acid occupies a central position in de nova pathways of phopholipid biosynthesis in Lung tissue as well a s other tissues T 2 5 ) 1 also was found that the specific activity of PAPase in the gastric aspirate or nasopharyngeal secretions of neonates a t birth was greater than that in samples of arnniotic fluid obtained from the same infants, a finding that provided strong evidence that the fetal tracheal fluid, i.e. fetal lung, is the source of the PAPase activity found in human amniotic fluid (10,12). In the present study we found that the specific activity of PAPase in ovine fetal tracheal fluid increased dramatically after 110 days of gestation; that is, after the completion of 80% of pregnancy.…”

“….4lihwgh the biosynthetic for the Droduction of the glycerophospholipids of surfactant have been Well rophospholipid biosynthesis (11,12,13,22). PAPase catalyzes the hydrolysis of rol (14).…”

“…The phospholipid was quantified by thi method of Parker and Peterson (17) as modified by Jimenez, e t al. (12).…”