Ontogeny of Surfactant Proteins A and B in Human Amniotic Fluid as Indices of Fetal Lung Maturity

Pryhuber, Gloria S.; Hull, William M.; Fink, Iris; McMahan, Michael; Whitsett, Jeffrey A.

doi:10.1203/00006450-199112000-00023

Cited by 146 publications

(98 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Total SP-B protein was analyzed by ELISA (15) and Western blotting (11,12), using equal amounts of protein from lung homogenates of 6 -7-week-old mice of each genotype. Mature SP-B, M r ϳ18,000, and SP-C, M r ϳ4,000, were separated by SDS-polyacrylamide gel electrophoresis in the absence of sulfhydryl reducing agents and detected by blotting with antiserum 28031 (11), which detects only SP-B, or antiserum 559 (13), which detects both SP-B and SP-C; SP-C proprotein was detected by antiserum 68514 (16) which recognizes antigenic determinants in the 20-amino acid N-terminal propeptide of SP-C.…”

Section: Generation and Identification Of Sp-b(ϫ/ϫ)/hsp-bmentioning

confidence: 99%

Rescue of SP-B Knockout Mice with a Truncated SP-B Proprotein

Akinbi

Breslin

Ikegami

et al. 1997

Journal of Biological Chemistry

View full text Add to dashboard Cite

Pulmonary surfactant is a complex mixture of lipids and proteins that is synthesized exclusively by the alveolar type II epithelial cell. Surfactant is stored in large inclusions (lamellar bodies) that are secreted into the alveolar airspace by exocytosis. Newly secreted lamellar bodies unravel into a tubular network (tubular myelin) that subsequently adsorbs and spreads as a phospholipid-rich film that reduces surface tension at the air-liquid interface. Rapid adsorption and spreading of the phospholipid film are critical and require the presence of specific proteins, in particular surfactant proteins B and C (1-3).Surfactant protein B (SP-B) 1 is a hydrophobic peptide of 79 amino acids that avidly associates with surfactant phospholipids in the alveolar airspace (reviewed in Ref. 4). Homozygous mutations leading to the complete absence of SP-B in newborn human infants result in the rapid onset of respiratory distress syndrome which is refractory to mechanical ventilation and surfactant replacement (5, 6). The latter observation suggests that simple addition of mature peptide to the SP-B-deficient airway is not sufficient to restore lung function. Therefore, despite an obvious requirement for SP-B in normal lung function, the precise role(s) of SP-B in the structure, function, and metabolism of surfactant remains unclear.Human SP-B is synthesized by the type II epithelial cell as a preproprotein of 381 amino acids. The mature peptide is generated by sequential cleavage of the signal peptide (23 amino acids), the N-terminal propeptide (177 residues), and the Cterminal propeptide (102 residues) (7, 8). Propeptide cleavage occurs within the late endosome/multivesicular body which subsequently directs newly synthesized SP-B to the lamellar body (9); mature SP-B is also recycled from the alveolar airspace, via the endocytic pathway to the multivesicular body (10). Previous in vitro evidence supports the concept that trafficking of the mature peptide through the biosynthetic pathway requires the N-terminal but not the C-terminal domain of the propeptide (11,12). In the absence of both propeptide domains the mature peptide is degraded within the endoplasmic reticulum (11); however, an SP-B construct encoding both the Nterminal propeptide and the mature peptide (hSP-B ⌬c ) produces a truncated proprotein that is sorted to the multivesicular body where the propeptide is appropriately cleaved to liberate mature SP-B (12). These results clearly demonstrate that the N-terminal propeptide is required for the intracellular trafficking of SP-B; the function of the C-terminal propeptide, however, remains unknown.Lung morphogenesis and surfactant phospholipid synthesis in SP-B(Ϫ/Ϫ) mice proceed normally prior to birth (13). However, lamellar body formation is disrupted, resulting in abnormal inclusions consisting of multivesicular bodies and disorganized lamellae. Neither mature lamellar bodies nor tubular myelin were detected in the SP-B(Ϫ/Ϫ) mice. In addition to effects on lamellar body biogenesis, SP-B deficiency resulted in

show abstract

Section: Generation and Identification Of Sp-b(ϫ/ϫ)/hsp-bmentioning

confidence: 99%

Rescue of SP-B Knockout Mice with a Truncated SP-B Proprotein

Akinbi

Breslin

Ikegami

et al. 1997

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…We measured the SP-A level in rat amniotic fluid using a sensitive ELISA, which showed an increase with advancing gestation after the initial appearance on day 18, but which was much lower than the level in human amniotic fluid, as reported by KUROKI et al [28] and PRYHUBER et al [15]. For example, the content of SP-A in rat amniotic fluid at the final gestational day 21 was 700±333 ng·ml -1 , which is about twentyfold lower than that in human amniotic fluid at the final gestational week [15,28].…”

Section: Discussionmentioning

confidence: 74%

“…For example, the content of SP-A in rat amniotic fluid at the final gestational day 21 was 700±333 ng·ml -1 , which is about twentyfold lower than that in human amniotic fluid at the final gestational week [15,28]. This result suggests that the flow quantity of SP-A into the amniotic cavity may be lower in rats than in humans, and that SP-A may be more rapidly metabolized in rat than human amniotic fluid.…”

Section: Discussionmentioning

confidence: 90%

“…SP-A in human amniotic fluid has also been assessed as a predictor of RDS [13][14][15]. However, it is unclear whether surfactant lipids and proteins have physiological functions in amniotic fluid.…”

Section: Discussionmentioning

confidence: 99%

“…As the foetal lung develops, SP-A also appears in human amniotic fluid, and is correlated with the presence of phospholipids. Therefore, SP-A is also useful in the prenatal assessment of lung maturity and as a predictor of RDS [13][14][15]. Although surfactant lipids and SP-A have important functions in the lung, it is not known whether they have physiological functions in amniotic fluid.…”

mentioning

confidence: 99%

See 2 more Smart Citations

A non-glycosylated form of pulmonary surfactant protein A appears in rat amniotic fluid

Sakai

Kohri²,

Kweon³

et al. 1994

Eur Respir J

View full text Add to dashboard Cite

Surfactant protein A (SP-A) is a family of glycoproteins that have a triplet with 26, 32 and 36 kDa under reducing conditions in rat lung. We wanted to evaluate the SP-A forms in amniotic fluid of pregnant rats compared to those found in rat lungs. By Western blot analysis, glycosylated SP-A, was not found in the amniotic fluid in contrast to the pulmonary surfactant triplet SP-A, which comprises a 26 kDa protein and its glycosylated 32 and 36 kDa forms. The SP-A concentration in amniotic fluid was barely detectable at 18 days of gestation (20 +/- 12 ng.ml-1), and then increased and reached 700 +/- 333 ng.ml-1 at the final gestational day 21, as determined by an enzyme-linked immunoabsorbent assay. Immunohistochemically, SP-A was found in some epithelial cells of larger respiratory bronchi, but not, or to a lesser degree, in smaller respiratory bronchi at gestational day 18. At 21 days of gestation, SP-A was detected in bronchial and bronchiolar nonciliated epithelial Clara cells, alveolar epithelial type II cells and some alveolar macrophages. The ratio of the 26, 32 and 36 kDa SP-A forms in bronchoalveolar, bronchobronchiolar and tracheal lavage fluids prepared from adult rats was 6:29:65, 84:5:11 and 100:0:0, respectively. These findings show the presence of a non-glycosylated SP-A in rat amniotic fluid. This may reflect the increased ratio of non-glycosylated SP-A to bronchoalveolar, bronchobronchiolar and tracheal lavage fluids, respectively.

show abstract