Placental expression of endothelial constitutive nitric oxide synthase mRNA in pregnancy complicated by preeclampsia

The role of nitric oxide (NO) in normal pregnancy and pregnancy complicated with preeclampsia (PE) and/or intrauterine growth restriction (IUGR) still remains questionable. The placenta lacks autonomic innervation, therefore blood flow must be regulated by humoral and endothelium derived factors. NO is a potent vasodilator released by endothelial cells. It is synthesized by the catalytic action of the endothelial constitutive nitric oxide synthase (ecNOS). Moreover, the synthesis of NO in normal human placental vasculature has already been established and impairment of the uteroplacental blood flow in pregnancies complicated by PE and/or IUGR has been demonstrated.

The aim of the present study was to compare the expression of ecNOS mRNA in placenta from women with complicated and normal pregnancies. Placenta was collected from women with PE (n = 13) or small for gestational age (SGA) (n = 8), both PE and SGA (n = 7) and normal pregnancies (n = 41). Total nucleic acids were prepared and a solution hybridization technique was used for mRNA analysis.

The mRNA expression of ecNOS was significantly higher (p<0.05) in all groups of complicated pregnancies compared to normal pregnancies.

Our findings indicate that the increased placental expression of ecNOS mRNA might reflect a compensatory mechanism in the disturbed uterine circulation seen in PE and/or SGA.