Decreasing resistance in the maternal uterine and peripheral arterial system is apparently unrelated to plasma and urinary levels of nitrite/nitrate and cyclic-guanosinmonophosohate during the course of normal pregnancies

Nitric oxide and peroxynitrite platelet levels in gestational hypertension and preeclampsia

The aim of the study was to investigate platelet nitric oxide (NO) pathways in women with Gestational Hypertension (GH), Preeclampsia (PE) and Controls. Platelet NO(x) and peroxynitrite (ONOO(-)) levels, inducible (iNOS) and endothelial nitric oxide synthase (eNOS) and Nitrotyrosine expression (N-Tyr) in 30 women with GH, 30 with PE and 30 healthy pregnant controls, age, parity and gestational age-matched, were assessed. Platelet NO(x) and ONOO(-) levels were significantly higher in GH and PE vs. Controls, with higher levels in GH vs. PE. At the same way, iNOS and N-Tyr were significantly higher in GH and PE vs. Controls, with higher levels in GH vs. PE. Since GH expressed higher amount of NO metabolites and higher activation of iNOS compared to PE, we can hypothesize that the severity of hypertensive pathology is almost not related to only NO metabolism, this research confirmed that GH and PE are associated with marked changes in NO pathways; it is not easy to understand if they could be interpreted as causes or consequence of these pathologic states.

Nitric oxide and peroxynitrite platelet levels in women with small-for-gestational-age fetuses

OBJECTIVE

The placenta produces reactive oxygen species (ROS) including nitric oxide (NO) and peroxynitrite (ONOO(-)) that have pronounced effects on placental function. Excessive ROS production may occur in pathological pregnancies, such as those complicated by small-for-gestational-age (SGA) fetuses.

DESIGN

The aim of the present work was to study NO and ONOO(-) levels in platelets of pregnant women with SGA fetuses compared with a control group.

SETTING AND POPULATION

The study was performed on 30 pregnant women with SGA fetuses (SGA group) and on 30 healthy pregnant women (appropriate-for-gestational-age [AGA] group) matched for maternal and gestational age. All women included in this study were in the third trimester of pregnancy.

METHODS

Platelets were isolated by differential centrifugation. NO metabolites, after enzymatic conversion followed by the Griess reaction, were measured as nitrite by spectrophotometric detection. Peroxynitrite (ONOO(-)) levels were evaluated using the fluorescence probe 2,7-dichlorofluorescein diacetate (DCFDA).

MAIN OUTCOME MEASURES

The following determinations were made: platelet nitric oxide and peroxynitrite levels in the SGA group and controls; inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS) and nitrotyrosine (N-Tyr) expression in the same groups.

RESULTS

Our results show that both platelet NO and ONOO(-) levels were significantly higher in the SGA group than in the controls.

CONCLUSION

Increased platelets levels of nitric oxide and peroxynitrite might play a role in the pathophysiology of intrauterine growth restriction. Further investigations are in progress to clarify if these molecules are pathogenetic factors, an epiphenomenon or a pathophysiological marker.

Plasma- and urine concentrations of nitrite/nitrate and cyclic Guanosinemonophosphate in intrauterine growth restricted and preeclamptic pregnancies

BACKGROUND

The Nitric Oxide (NO) system plays an important role in the establishment and maintenance of the feto-placental circulation. Research on the pathogenesis of preeclampsia in several studies has established the involvement of the NO-system in preeclampsia and fetal intrauterine growth restriction (IUGR). In the presented study we analyzed the urine and plasma concentrations of nitrite/nitrate, the stable endproducts of NO and its second messenger, cyclic Guanosinemonophosphate (cGMP) in normal, preeclamptic and IUGR pregnancies.

PATIENTS AND METHODS

In total 76 patients were investigated in a prospective study for repeated determination of plasma and urinary levels of nitrate/nitrite and cGMP: 49 patients with a normal course of pregnancy, 14 patients with fetal IUGR and 13 patients with preeclampsia were included into the study. Plasma and urine Nitrite/Nitrate-concentrations were determined using a Colorimetric Assay (Cayman Inc., USA), concentrations of the second messenger cGMP in plasma and urinary samples were determined with a J(125)-Radio-Immuno-Assay (ibl Inc., Germany). The Stat View Program (Abacus Concepts, Inc., Berkeley, CA, 1992-1998) was used for statistical analysis, a P value <0.05 was considered significant.

RESULTS

Analyzing the data with the Kruskall-Wallis test a significance was reached for Plasma Nitrite/Nitrate (P=0.0236), plasma cGMP (P=0.004) and urinary nitrite/nitrate (P=0.032). No significance was seen for urinary cGMP (P=0.656). Comparing normal and preeclamptic and normal and IUGR pregnancies the following significant differences were seen (Mann-Whitney U test): In preeclamptic pregnancies urine nitrite/nitrate concentration was significantly lower compared to normal pregnancies (P=0.009) No significant difference between normal and preeclamptic pregnancies for plasma nitrite/nitrate (P=0.819) and plasma-cGMP (P=0.072) could be observed. In IUGR pregnancies plasma nitrite/nitrate and the plasma-cGMP concentrations were both significantly lower compared to normal pregnancies (P=0.0077 and 0.0066) in IUGR-pregnancies. No significance was reached when analyzing urine-Nitrite/Nitrate (P=0.7).

CONCLUSION

Whereas in preeclampsia a reduced urinary nitrite/nitrate was analyzed, IUGR pregnancies showed reduced plasma nitrite/nitrate and cGMP. A reduced release of NO into the maternal circulation might lead to the presented findings and be involved in the pathogenesis of preeclampsia and fetal IUGR.

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

Pregnancy and the follicular phase of the ovarian cycle show elevation of uterine blood flow and associated increases in uterine artery endothelium (UAE) endothelial nitric oxide (NO) synthase (eNOS) expression. Nonetheless, a role for increased NO production during pregnancy and the follicular phase has only been inferred by indirect measures. The recent development of a uterine artery endothelial cell model further suggests that pregnancy is associated with reprogramming of cell signaling, such that eNOS may become more Ca(2+) sensitive and be subject to regulation by Ca(2+)-independent kinases. This study describes for the first time the direct and simultaneous monitoring of NO production and intracellular free Ca(2+) concentration ([Ca(2+)](i)) in freshly isolated UAE from pregnant, follicular, and luteal sheep. The pharmacological agonists ionomycin (calcium ionophore) and thapsigargin (TG; endoplasmic reticulum Ca(2+) pump inhibitor) were used to maximally elevate [Ca(2+)](i) and fully activate eNOS as a measure of eNOS expression. NO production stimulated by ionomycin (5 microM) and TG (10 microM) were 1.95- and 2.05-fold, respectively, in pregnant-UAE and 1.34- and 1.37-fold in follicular-UAE compared with luteal-UAE. In contrast, the physiological agonist ATP (100 microM) stimulated a 3.43-fold increase in NO in pregnant-UAE and a 1.90-fold increase in follicular-UAE compared with luteal-UAE, suggesting that pregnancy and follicular phase enhance eNOS activation beyond changes in expression in vivo. 2-aminoethoxydiphenyl borate (APB; an inositol 1,4,5-trisphosphate receptor blocker) totally prevented the ATP-induced [Ca(2+)](i) response but only partially inhibited NO production. Thus pregnancy-enhanced eNOS activation in UAE is mediated through [Ca(2+)](i)-insensitive pathways as well as through a greater eNOS sensitivity to [Ca(2+)](i).