Immunolocalization of the inducible nitric oxide synthase isoform in human fetal membranes.
OBJECTIVE
Nitric oxide (NO) synthesized by fetal membranes may protect the fetus from maternal infection or immune challenge or have a tocolytic effect on myometrium. The sites of synthesis and enzymes responsible for NO production in human fetal membranes remain unidentified.


METHODS
Fetal membranes were obtained from four groups of patients: term (> 37 weeks gestation) or preterm (< 37 weeks gestation), both either in labor or not in labor. Frozen sections of membrane rolls were immunostained for inducible (iNOS) and endothelial (eNOS) nitric oxide synthase isoforms and the monocyte/macrophage marker CD14.


RESULTS
Positive iNOS immunostaining was found in fibroblasts of amnionic and chorionic mesenchyme and in decidual macrophages identified by CD14 from all four groups of tissues. No iNOS immunostaining was seen in amnion epithelium or chorion trophoblast. Very intense iNOS staining was seen with evidence of monocyte/macrophage invasion of membranes. eNOS immunostaining was only found in decidual vascular endothelium.


CONCLUSIONS
Constitutive expression of iNOS in decidual macrophages and fetal membrane fibroblasts may form an immune barrier against maternal insult. In chorioamnionitis, macrophage recruitment and NO expression may be part of the maternal immune response.
Eis
A L
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Department of Obstetrics and Gynecology, University of Cincinnati College of Medicine, OH 45267-0526, USA.
Brockman
D E
DE
Myatt
L
L
D004730:Endothelium, Vascular / Q000201:enzymology / Q000276:immunology; D005321:Extraembryonic Membranes / Q000098:blood supply / Q000201:enzymology* / Q000276:immunology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007231:Infant, Newborn; D007743:Labor, Obstetric / Q000276:immunology / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000276:immunology / Q000378:metabolism*; D007752:Obstetric Labor, Premature / Q000201:enzymology / Q000276:immunology; D011247:Pregnancy
D018950:Lipopolysaccharide Receptors; D019001:Nitric Oxide Synthase