A non-glycosylated form of pulmonary surfactant protein A appears in rat amniotic fluid.
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.
Sakai
K
K
Dept of Nutrition, School of Medicine, University of Tokushima, Japan.
Kohri
T
T
Kweon
M N
MN
Kishino
Y
Y
D000653:Amniotic Fluid / Q000737:chemistry*; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005333:Fetus / Q000378:metabolism; D005865:Gestational Age; D006031:Glycosylation; D007150:Immunohistochemistry; D008168:Lung / Q000737:chemistry; D008297:Male; D051381:Rats; D013047:Specific Pathogen-Free Organisms; D013205:Staphylococcal Protein A / Q000032:analysis*
D013205:Staphylococcal Protein A