Gene Expression of Nitric Oxide Synthase and Heme Oxygenase in Placental Villi during Pregnancy with and without Intrauterine Growth Restriction

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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.