Plasma Nitric Oxide Levels in Pregnant Patients with Preeclampsia and Essential Hypertension

Abstract

Nitric oxide (NO) production may be an important causal factor in hypertensive disorders during pregnancy. The plasma concentrations of NO₂^––+NO₃^––, stable metabolites of NO, were measured in 70 nonpregnant women, 323 normotensive pregnant women, 23 pregnant patients with preeclampsia, and 7 pregnant patients with essential hypertension. The normotensive women had higher plasma concentrations (30.0 ± 0.6 µmol/l) than nonpregnant women (18.3 ± 1.0 µmol/l; p < 0.0001). The plasma concentrations in the patients with preeclampsia (45.6 ± 2.3 µmol/l) were higher than in the normotensive women (30.3 ± 1.0 µmol/l; p < 0.0001) and were correlated with the systolic blood pressure (r = 0.442; p < 0.05). However, pregnant patients with underlying essential hypertension had significantly lower plasma concentrations (19.1 ± 3.0 µmol/l; p < 0.005). These findings suggest that NO contributes to maternal vasodilation, the maintenance of uterine quiescence, and the pathogenesis and clinical features of hypertensive disorders during pregnancy.

Maternal Circulating Nitrite Levels Are Decreased in both Normal Normotensive Pregnancies and Pregnancies with Preeclampsia

“…With respect to the comparison of nitric oxide synthesis between nonpregnant and pregnant women in previous studies [11,18], serum nitrite or plasma nitrite and nitrate concentrations in normotensive pregnant women were significantly elevated as compared with those in the normotensive nonpregnant women. However, Smarason et al [22] reported that there is no significant difference in serum nitrate concentration between healthy pregnant women and nonpregnant controls.…”

“…Yallampalli et al [10] show that an L-arginine-nitric oxide relaxation system is present in the rat uterus and it inhibits contractility during pregnancy but not during labor. Plasma nitrite and nitrate concentrations in normotensive pregnant women was constant throughout pregnancy, and significantly elevated as compared with the normotensive nonpregnant women [11]. On the other hand, endogenous nitric oxide production does not play an important role in the control of human term or preterm nonlaboring uterine smooth muscle contractility [12].…”

Magnesium sulfate therapy of preeclampsia: an old tool with new mechanism of action and prospect in management and prophylaxis

“…28 In addition, the NO signaling pathway, the vasodilator and antiplatelet effects of NO are expected to decrease vascular tone and increase placental blood flow, leading to better fetal nutrients and oxygen supply. 42 This expectation explains the increased fetal viability and birth weight in the MgSO 4 -treated group. The reduction of circulating antiangiogenic factors in the PRE þ MgSO 4 group in the current study could be explained by the ability of MgSO 4 to decrease systemic vascular resistance and counteract the vasoconstrictor substances in several vascular beds.…”

Simultaneous imaging of [Ca2+]iand intracellular NO production in freshly isolated uterine artery endothelial cells: effects of ovarian cycle and pregnancy

“…However, the physiological role of NO in pregnancy and follicular phase remains controversial owing to the lack of direct NO measurement (11,37,39). By simultaneously monitoring [Ca 2ϩ ] i and NO levels in the freshly isolated endothelium of UAs, we report the first direct evidence that pregnant, follicular, and L endothelial cells have different abilities to produce NO in response to pharmacological and physiological [Ca 2ϩ ] i agonists.…”