The Concentration of the 35-kDa Surfactant Apoprotein in Amniotic Fluid from Normal and Diabetic Pregnancies

Abstract

ABSTRACT. A specific, enzyme-linked immunoabsorbent assay was used to determine the concentration of the 35,000 mol wt surfactant apoprotein (SP-A) in samples of amniotic fluid obtained from nondiabetic (n = 358) and diabetic (n = 29) women. The enzyme-linked immunoabsorbent assay was performed with rabbit antibodies directed against SP-A present in lavage fluid from a patient with alveolar proteinosis. Amniotic fluid SP-A concentrations increased as a function of gestational age, from <3 jtg/ml at 30-31 wk to 24 pg/ml at 40-41 wk, and were positively correlated with the lecithin to sphingomyelin ratio ( p < 0.01). SP-A concentrations also increased as a function of gestational age in shake test positive samples ( p < 0.05), but were unchanged in shake test-negative samples. There was no difference in the surfactant apoprotein concentration of male compared with female fetuses at any gestational age. In amniotic fluid obtained from 20 diabetic women, SP-A levels were significantly less than in nondiabetic pregnancies that were matched for gestational age and sex of the fetus ( p < 0.05). The SP-A concentrations in amniotic fluids obtained from nine women who were diabetic and hypertensive and from 10 hypertensive women were not different from matched controls. The relationships described above were valid whether the SP-A concentration was expressed per mg protein or per ml amniotic fluid. These data are suggestive that the concentration of amniotic fluid SP-A is decreased in diabetic pregnancies. (Pediafr Res 24: 728-734, 1988)

Surfactant protein secreted by the maturing mouse fetal lung acts as a hormone that signals the initiation of parturition

“…Like SP-A, the related collectin SP-D is developmentally regulated in fetal lung late in gestation, reaching maximal levels at term (35,36). SP-D protein also is evident in human amniotic fluid although its levels increase only modestly after 32 weeks of gestation (37), in contrast to the pronounced rise in SP-A (20,37). Although SP-D levels remained unchanged in lung tissues of adult transgenic mice that overexpressed recombinant SP-A (34) and in adult SP-A null mice (33), no information was provided regarding SP-D levels in the fetal lungs.…”

“…Human AF SP-A levels increase from Ͻ3 g͞ml at 30 weeks gestation to Ͼ24 g͞ml at term (20). SP-A expression in human fetal lung is stimulated by IL-1 acting through NF-B (21) and by cAMP (21,22).…”

“…AF levels of SP-A, compared with known concentrations of purified SP-A by immunoblotting, were determined to be Ϸ30 g͞ml at 19 dpc (data not shown). In human pregnancy, AF levels of SP-A increase from Ͻ3 g͞ml at 30 weeks gestation to Ͼ24 g͞ml at term (20). We postulated that SP-A may interact with AF macrophages, inducing their activation and migration to the maternal uterus.…”

Surfactant Protein A Binds to HIV and Inhibits Direct Infection of CD4+ Cells, but Enhances Dendritic Cell-Mediated Viral Transfer

“…Levels in BAL fluids are ϳ2.82 g/ml (40), whereas concentrations in situ in the lung in association with lung surfactant are considerably higher. SP-A levels have also been shown to be elevated to 6 g/ml in HIV-infected BAL (41) and have been shown to be as high as 24 g/ml in amniotic fluid at term (42), when SP-A acts as signal for parturition (43). Levels of SP-A in the vaginal tract have yet to be definitively determined, and the collectin likely makes up only a part of the milieu of defense proteins that include human ␤-defensins, lysozyme, lactoferrin, and human neutrophil peptides which have already been shown to inhibit HIV infection (44).…”

Role of fetal membranes in signaling of fetal maturation and parturition

“…Glucocorticoids accelerate lung maturation by enhancing surfactant synthesis in the pulmonary alveolar cells (Gonzales et al, 1986;Snyder et al, 1981). During fetal development, the type II alveolar cells of fetal lung eventually synthesize and release surfactant into pulmonary secretions (Van Golde et al, 1988), which is intermittently discharged into the amniotic fluid (Pryhuber et al, 1991;Snyder et al, 1988). Surfactant is a complex mixture consisting of phospholipids, nonpolar lipids, and proteins (Van Golde et al 1988;Floros and Phelps 1997).…”