Immunohistochemical localization of inducible nitric oxide synthase on human fetal amnion in intra-amniotic infection.
OBJECTIVE
Amniotic fluid levels of nitric oxide metabolites are significantly elevated in intra-amniotic infection. We hypothesized that fetal amnion is a possible site for the production of nitric oxide. Because inducible nitric oxide synthase is the key enzyme responsible for the generation of nitric oxide in patients with intra-amniotic infection, we used immunohistochemistry to localize it on human fetal amnion.


METHODS
Human fetal amnions were obtained from patients with and without intra-amniotic infection (n = 5, respectively). Intra-amniotic infection was diagnosed by positive amniotic fluid cultures and placental pathologic features. Human fetal amniotic membranes were processed into tissue blocks and embedded in paraffin. A rabbit polyclonal antibody against human inducible nitric oxide synthase was used as the primary antibody, followed by avidin-biotin immunoperoxidase localization. Normal rabbit serum was used as a negative control and ovarian carcinoma cells were used as the positive control.


RESULTS
Anti-inducible nitric oxide synthase labeling of human fetal amniotic membranes in patients with intra-amniotic infection showed positive immunostaining of epithelial cells, specifically in the cytoplasm of the perinuclear area. In contrast, no anti-inducible nitric oxide synthase immunostaining on human fetal amniotic membranes could be identified in patients without intra-amniotic infection.


CONCLUSIONS
Our data provide important evidence that inducible nitric oxide synthase can be induced on human fetal amnion in intra-amniotic infection. These findings strongly support our hypothesis that human fetal amnion may be a possible site for the synthesis of nitric oxide after inducible nitric oxide synthase is induced in response to infectious products in intra-amniotic infection.
Hsu
C D
CD
Departments of Obstetrics and Gynecology and Pathology, Yale University School of Medicine, New Haven, Connecticut, USA.
Meaddough
E
E
Lu
L C
LC
Chelouche
A
A
Liang
R I
RI
Copel
J A
JA
Parkash
V
V
D000650:Amnion / Q000201:enzymology* / Q000382:microbiology*; D000818:Animals; D005260:Female; D005333:Fetus / Q000201:enzymology*; D006801:Humans; D007150:Immunohistochemistry; D007239:Infections / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000201:enzymology* / Q000382:microbiology; D011817:Rabbits; D014018:Tissue Distribution
C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II