Objective: Preeclampsia is a syndrome involving dysfunction of vascular endothelium and imbalance between endothelium derived constricting and relaxing factors. Recent evidence suggests that endothelium-derived nitric oxide (NO) plays a role in the regulation of vascular resistance during normal pregnancy and preeclampsia. NO is a potent vasodilator and is generated by the catalytic action of nitric oxide synthases ecNOS and iNOS in myometrium and placenta.
Methods: In this study mRNA expressions of ecNOS and iNOS were compared in myometrium and placenta. Biopsies were collected from women with preeclampsia (n=8) and normal pregnancies (n=12). ecNOS and iNOS mRNA levels were determined using RT-PCR and expressed as arbitrary units after correction for control GAPDH gene mRNA levels.
Results: The mRNA expression of ecNOS was significantly higher in both myometrium (p<0.05) and placenta (p<0.05) from women with preeclampsia compared to that in normal pregnancies, while the iNOS mRNA level was not altered in myometrium and lower in placenta (p<0.05) from women with preeclampsia.
Conclusions: The higher ecNOS mRNA expression might be a compensatory response to an impaired vasodilatation in the uteroplacental circulation during preeclampsia. Whether the similar and reduced levels of iNOS mRNA expression in myometrium and placenta, respectively, in women with preeclampsia is of importance remains to be further evaluated.