Gene expression of nitric oxide synthase and heme oxygenase in placental villi during pregnancy with and without intrauterine growth restriction

It is commonly accepted that the intrauterine growth restriction (IUGR) is correlated with an impairment of utero-placental blood flow. This blood flow is regulated by prostaglandins and nitric oxide (NO), which regulate vascular tone in placental villi. The factors that regulate utero-placental blood flow play different functions independently, and their functions differ according to the gestational stage. To evaluate the influence of NO and carbon monoxide (CO) on the feto-maternal circulation, we quantified endothelial NO synthase (eNOS) and heme oxygenase (HO) type 1 (HO-1) mRNAs in the placental villi. Forty-three placental samples were employed. We measured both eNOS and HO-1 mRNAs by Northern blot hybridization. The eNOS mRNA expression in the first trimester (relative intensity, 3.741+/-0.679, mean+/-SEM) was higher than that after the first trimester (0.500+/-0.038, p<0.0001). The HO-1 mRNA expression in the third trimester was higher than that before the third trimester (2.648+/-0.409 and 1.122+/-0.182, respectively, p<0.005). There was no difference in the expression of eNOS and HO-1 mRNAs between pregnancies with or without IUGR. Independent expression of eNOS and HO-1 mRNAs suggests that eNOS is important in placentation at early gestation, whereas HO-1 is important in maintenance of pregnancy for the term.