Stimulated nitric oxide release and nitric oxide sensitivity in forearm arterial vasculature during normotensive and preeclamptic pregnancy

OBJECTIVE: We sought to determine whether the enhanced forearm vascular activity of nitric oxide during pregnancy and preeclampsia is associated with altered smooth muscle sensitivity to nitric oxide or with stimulated nitric oxide release. STUDY DESIGN: Forearm blood flow responses to brachial artery infusion of glyceryl trinitrate (a nitric oxide donor), serotonin (an endothelium-dependent nitric oxide-mediated agonist), and ritodrine (a beta-adrenergic receptor agonist) were studied in 10 nonpregnant women, 12 pregnant women, and 7 women with preeclampsia by means of strain-gauge plethysmography. Responses to each drug (maximum dilator response and the sum of the percentage of dilator responses to each drug) were compared by analysis of variance. RESULTS: Compared with nonpregnant women, pregnant subjects showed reduced responses to serotonin (summary response, 117 +/- 19 vs 221 +/- 30; P <.05). Responses to serotonin were reduced in the group with preeclampsia compared with those in the nonpregnant group (summary response, 71 +/- 28; P <.05) but did not differ from the responses in pregnant women. There were no differences between responses to glyceryl trinitrate and responses to ritodrine in any of the groups. CONCLUSION: Vascular smooth muscle sensitivity to nitric oxide is not altered in normal pregnancy or preeclampsia, but dilator responses to serotonin appear blunted. Alterations in serotonin receptor coupling to nitric oxide synthase, or a limitation of availability of the substrate for nitric oxide synthase (L-arginine) during pregnancy, could account for the reduction in stimulated nitric oxide release.     

Cervical nitric oxide release in women postterm

OBJECTIVE: Nitric oxide may be a factor in cervical ripening. We compared the nitric oxide metabolite levels in cervical fluid in women going beyond term and in women delivering spontaneously at term. METHODS: We studied a total of 208 women with singleton pregnancies: 108 women who went beyond term (294 days or longer), and 100 women who went spontaneously into labor at term. Cervical fluid samples, collected well before the initiation of labor, were assessed for nitric oxide metabolites using an assay with a detection limit of 3.8 micromol/L. RESULTS: Women going beyond term had detectable levels of nitric oxide metabolites in their cervical fluid (60%) less often (P =.001) than women delivering at term (87%). The nitric oxide metabolite concentration in cervical fluid in women going beyond term (median 23.5 micromol/L; 95% confidence interval less than 3.8, 31.8) was 4.5 times lower (P <.001) than that in women delivering at term (median 106.0 micromol/L; 95% confidence interval 81.8, 135.0). Such a difference (14.0 versus 106.0 micromol/L) also existed when only the 66 women going into spontaneous postterm labor were included in the comparison. Both nulliparous (median less than 3.8 micromol/L) and parous (median 31.3 micromol/L) women going beyond term had lower (P <.01) cervical fluid nitric oxide metabolite levels than nulliparous and parous women delivering at term (medians 76.1 and 101.3 micromol/L, respectively). In the postterm group, women with cervical fluid nitric oxide metabolite concentrations at or below the median failed more often (P <.001) to progress in labor and had longer (P =.02) duration of labor than those with cervical fluid nitric oxide metabolite concentrations above the median. CONCLUSION: Reduced cervical nitric oxide release may contribute to prolonged pregnancy. LEVEL OF EVIDENCE: II-2     

Serum nitric oxide and glutathione levels in preeclamptic and normotensive women during labor

This study was performed on 38 preeclamptic women, including 26 severely preeclamptic and eclamptic cases, as well as 50 normotensive pregnant controls. Twenty cases in the preeclamptic group and 34 cases in the control group were in labor. Serum nitric oxide levels were measured as total nitrites after reduction of nitrates to nitrites. Among the control subjects, nitric oxide levels were significantly lower in the cases in labor when compared to those not in labor (p < 0.05), but glutathione levels were not significantly different (p >0.05). Among the preeclamptic patients, although nitric oxide levels were not significantly different between the cases in and not in labor (p > 0.05), glutathione levels were significantly higher in the latter group (p < 0.05). Thus, in preeclamptic patients there might be a compensatory increase in nitric oxide production during labor in order to maintain the systemic circulation. Glutathione levels might also be increased to compensate for the marked oxidative stress.     

The correlation between renal function and systolic or diastolic blood pressure in severe preeclamptic women.

OBJECTIVE: To evaluate the correlation between renal function and systolic or diastolic blood pressure in preeclamptic mothers. METHODS: In this prospective study from August 1998 to September 2002, 28 women >or= 28 weeks gestation with severe preeclampsia were selected. Meanwhile, 56 normotensive pregnant women without proteinuria or edema served as the control group. Urine was collected for 24 hours for all subjects. The concentration of uric acid, blood urea nitrogen, creatinine, sodium, calcium, and albumin in the 24-hour urine and blood of both groups were examined. Neonatal outcome also was evaluated. RESULTS:The serum and 24-hour urine concentration of blood urea nitrogen, creatinine, and albumin were significantly higher in severe preeclamptic women. Serum uric acid and urinary albumin/creatinine ratio was significantly higher in severe preeclamptic women compared with that in normotensive mothers and showed positive correlation with systolic or diastolic blood pressure. On the other hand, serum calcium/creatinine ratio was significantly lower in the severe preeclamptic group and negatively correlated to blood pressure. In multiple regressions, systolic or diastolic blood pressure was dependent on serum uric acid, albumin/creatinine, and calcium/creatinine ratios. Fetal birth weight was significantly lower in women with severe preeclampsia and with a lower Apgar score < 7 at 1 minute and 5 minutes and more preterm delivery compared with that in normotensive women. CONCLUSION: Renal function in women with severe preeclampsia was significantly impaired and highly correlated with systolic or diastolic blood pressure.     

Clinical use of nitric oxide donors and L-arginine in obstetrics.

Nitric oxide (NO) is a free radical that plays a fundamental role in human physiology, being involved in the homeostasis of different functions. In obstetrics this molecule is determinant in the physiology of labor and cervical ripening; it possibly plays a fundamental role in the etiology of preeclampsia and intrauterine growth restriction, and it could also be utilized in view of its ability to induce smooth muscle relaxation. Several clinical trials have ascertained the ability of the topical application of NO donors to promote cervical ripening, and also labor induction. There is much less evidence on the use of NO donors in the vascular complications of pregnancy, either as prophylactics or therapeutic agents. Due to the capacity of NO to promote relaxation of smooth muscle, NO donors have been employed as tocolytics with performance similar to other agents. Moreover, although anecdotal, the experience of sudden uterine relaxation using NO donors in obstetric emergencies remains of great clinical value.     

Plasma nitric oxide metabolites and lipid peroxide levels in preeclamptic pregnant women before and after delivery

The glutathione S-transferases (GSTs) are a family of isoenzymes with several functions. These include the metabolism of endogenous and exogenous toxic compounds, an isomerase activity in steroidogenesis and intracellular transport. This study has used immunohistochemistry to demonstrate the distribution of the three classes of GST (alpha, mu and pi) in the human ovary at different stages of the menstrual cycle. Alpha-GST was found in cells related to steroid hormone production and probably acts as a delta4-5 isomerase. Mu-GST was predominantly found in the non-luteinized stromal cells and its function is obscure. Pi-GST was found in surface 'epithelial' inclusions and the media of arteries where it is thought to play a detoxifying role.     

Short-term effect of magnesium sulfate infusion on renal function in preeclamptic women.

Magnesium (Mg) plays an important role in cardiovascular homeostasis. A deficiency may be of importance for the etiology of disorders that have vasospasm in common. Mg administration can reduce the peripheral vascular resistance and thus enhance organ perfusion. We observed that Mg sulfate infusion could have a beneficial effect upon the serum urate concentration in preeclamptic women, presumably by affecting the renal function. A study comprising 10 preeclamptic women with a high serum urate level (413-788 umol/l) was carried out. Glomerular filtration rate (GFR) was measured by determination of iohexol clearance. 30 mmol Addex-Magnesium was then given i.v. during 12 h and a second GFR determination performed the next day. We had expected the GFR to increase, but to our surprise, it decreased (in mean, from 74.2 ml/[min x 1.73 m2] to 71.3; p < 0.05; Wilcoxon signed-ranks test). There were no significant changes of blood pressure, proteinuria, blood thrombocytes, transaminases, serum creatinine or serum urate. We conclude that in preeclamptic women with renal dysfunction, Mg infusion therapy had no favourable effect upon either blood pressure nor GFR in the short-term perspective.     

Effects of acute L-arginine infusion on non-stress test in hypertensive pregnant women.

OBJECTIVE: The present report evaluates the effect of acute L-arginine administration on fetal heart variables by a computerized non-stress test (NST) analysis. METHODS: Fifteen pregnant women at 30-34 weeks of gestational age affected by mild to moderate gestational hypertension were enrolled in the study. The study was performed in the second and third days of hospitalization. Each woman received both active (Arg) or placebo treatment (Placebo), in a double-blind, randomized, cross-over design. Women received saline infusion for 40 min, then they were infused with either placebo (saline infusion prepared by Damor Pharmaceutics and labeled as Arg-B) or Arg (L-Arg 20 g/500 ml labeled as Arg-A). RESULTS: Multiple analysis of variance (MANOVA) indicated that both placebo and Arg infusion were unable to affect cardiac variables and fetal movements. As far as maternal blood pressure changes were concerned, MANOVA indicated that active treatment showed an acute hypotensive effect on both systolic (F=8.98, p<0.001) and diastolic values (F=15.78, p>0.001). Conversely, placebo infusion does not seems to have induced any change. Considering each time of infusion we observed that Arg treatment was able to lower systolic and diastolic blood pressure after the 40 min of infusion, with this effect persisting for 20 min. CONCLUSIONS: These data indicate that the acute, intravenous administration of high-dose L-arginine does not induce significant changes in fetal heart rate (FHR), whereas it lowers maternal blood pressure. Such conclusions are reinforced by the observation that saline administration in the same pregnant women was neutral for both FHR and maternal blood pressure values. According to previous studies, it seems conceivable that maternal L-arginine treatment enters the fetal circulation by crossing the placenta. The lack of changes in FHR, however, suggests that no significant hemodynamic changes were induced by the treatment. Contrary to what happens in the mother, this may possibly be due to a low, if any, conversion of L-arginine to nitric oxide in the fetus.     

Endothelial nitric oxide synthase (eNOS) gene Glu298Asp polymorphism and expression in North Indian preeclamptic women

BackgroundPathophysiological processes in preeclampsia (PE) are influenced by genetic factors, nitric oxide synthases seem to play important roles, although their expression in and their role is still unclear. To better characterize the host genetic factors determining the susceptibility to PE, we evaluated the influence of polymorphisms (Glu298Asp) in the endothelial nitric oxide synthase (eNOS) gene on the risk of developing PE by checking the expression level.MethodsWe conducted a hospital-based case-control study including 300 women with preeclampsia and 200 healthy pregnant women. Their blood samples were analyzed for levels of nitric oxide, eNOS gene polymorphism and expression. eNOS mRNA levels were determined using RT-PCR and expressed as arbitrary units after correction with control β-Actin gene mRNA levels.ResultsThe mRNA expression of eNOS gene was found to be significantly lower in blood (P < 0.05) from women with PE compared to that from normal pregnancies. The total nitric oxide levels (P < 0.001) were decreased in study Group as compared to healthy pregnant patients. The intergenotypic variation of nitric oxide levels in preeclamptic women was found to be significant (P < 0.001).ConclusionsThese results indicate the relationship between reduced nitric oxide levels and eNOS gene polymorphism leading to its altered expression in preeclamptic women.     

Effect of L-arginine load on platelet aggregation: a comparison between normotensive and preeclamptic pregnant women.

BACKGROUND: In the present study we hypothesized that a derangement of the L-arginine-nitric oxide system could be involved in the development of the hypercoagulative status found during preeclampsia. In order to verify such hypothesis we have compared the effects of nitric oxide substrate, L-arginine on platelet aggregation. Moreover, we have also measured the L-citrulline plasma levels as a stochiometric metabolite resulting from the conversion L-arginine to nitric oxide. METHODS: Nine preeclamptic women and 11 normotensive pregnant women were enrolled for the study. Subjects were infused with saline and with 30gr of L-arginine. Blood samples were drawn during the saline infusion (30 min), during L-arginine administration (30 min) and 30 min thereafter. ADP and collagen-induced platelet aggregation was studied as per Born with a dual-channel aggregometer (Chrono-Log, Mascia Brunelli, Italy) and L-citrulline was measured by HPLC. RESULTS: In normotensive women the infusion significantly decreased ADP and collagen-induced aggregation after 15 minutes of L-arginine load; whereas no effects were observed in preeclamptic women. Similarly in normotensive but not in preeclamptic women L-arginine load was able to increase L-citrulline plasma levels. CONCLUSIONS: In normotensive women the in vivo L-arginine administration decreases platelet aggregation with an increase of L-citrulline plasma levels. On the contrary, no effects were observed in preeclamptic women. These findings confirm that a hypercoagulative status characterizes preeclampsia and that such phenomenon could be explained by a derangement of the platelet L-arginine-nitric oxide pathway.     

The VNTR polymorphism of the endothelial nitric oxide synthase gene and blood pressure in women at the end of pregnancy

ObjectiveExamine the association of the 4a/4b polymorphism of endothelial nitric oxide synthase (eNOS) with blood pressure in women at late pregnancy.Materials and methodsBlood pressure before pregnancy and at the end of gestation (37–40-week term) was measured in 588 women of the Russian ancestry. The women were divided into groups according to the body mass index and the presence of preeclampsia at late pregnancy. The 4a/4b polymorphism of the eNOS gene was genotyped using PCR with subsequent screening of amplified fragment length polymorphisms.ResultsThe 4a4a eNOS genotype was associated with higher levels of diastolic blood pressure in pregnant women and with more pronounced dynamics of the diastolic and mean arterial pressure in the development of pregnancy (p = 0.02–0.03). Pregnant women with the 4a4a genotype and increased body mass index had higher systolic, diastolic, and mean arterial pressure (p = 0.001–0.009). In pregnant women with preeclampsia, the 4a4a genotype was associated with higher level of diastolic blood pressure at the end of pregnancy (p = 0.04), whereas in the women without preeclampsia this genotype was associated with more pronounced changes of blood pressure at pregnancy (p = 0.02).ConclusionThe results of our study suggest that the genotype 4a4a of the eNOS gene is associated with higher levels of blood pressure in women at the end of pregnancy.     

Modulatory effect of blood cells on hypoxic vasoconstriction response and nitric oxide release in rat lungs.

In this study, we investigated the modulatory effects of different types of blood cells on hypoxic pulmonary vasoconstrictive (HPV) response and nitric oxide (NO) release in isolated rat lungs. The lungs were perfused at a constant flow with physiologic saline solution (PSS). The changes in pulmonary arterial pressure (PAP) and NO release were observed. Two hypoxic challenges with a 5% CO2-95% N2 gas mixture were carried out in each experiment. Hypoxia induced pulmonary vasoconstriction, as reflected by an increase in PAP (0.88 +/- 0.22 cmH2O). At the same time, NO (342.9 +/- 78.3 mv) release from the lungs was also increased. Addition of white blood cells (WBCs, 0.70 to 0.88 x 10(5)/mL), platelets (1.48 to 1.96 x 10(5)/mL), or red blood cells (RBCs, 4.6 to 6.6 x 10(5)/mL) into the perfusate produced different effects on PAP and NO changes. WBCs decreased the pulmonary vasoconstriction response and this was accompanied by an increase in NO release. Platelets had no significant effects on either PAP or NO. RBCs significantly potentiated the PAP increase and attenuated the NO release. The results indicate that NO release during hypoxia tends to offset pulmonary vasoconstriction and that NO release and HPV response are modulated by different cell elements.     

Effects of acute L-arginine infusion on non-stress test in hypertensive pregnant women

Objective: The present report evaluates the effect of acute L-arginine administration on fetal heart variables by a computerized non-stress test (NST) analysis.

Methods: Fifteen pregnant women at 30–34 weeks of gestational age affected by mild to moderate gestational hypertension were enrolled in the study. The study was performed in the second and third days of hospitalization. Each woman received both active (Arg) or placebo treatment (Placebo), in a double-blind, randomized, cross-over design. Women received saline infusion for 40?min, then they were infused with either placebo (saline infusion prepared by Damor Pharmaceutics and labeled as Arg-B) or Arg (L-Arg 20?g/500?ml labeled as Arg-A).

Results: Multiple analysis of variance (MANOVA) indicated that both placebo and Arg infusion were unable to affect cardiac variables and fetal movements. As far as maternal blood pressure changes were concerned, MANOVA indicated that active treatment showed an acute hypotensive effect on both systolic (F?=?8.98, p?<?0.001) and diastolic values (F?=?15.78, p?>?0.001). Conversely, placebo infusion does not seems to have induced any change. Considering each time of infusion we observed that Arg treatment was able to lower systolic and diastolic blood pressure after the 40?min of infusion, with this effect persisting for 20?min.

Conclusions: These data indicate that the acute, intravenous administration of high-dose L-arginine does not induce significant changes in fetal heart rate (FHR), whereas it lowers maternal blood pressure. Such conclusions are reinforced by the observation that saline administration in the same pregnant women was neutral for both FHR and maternal blood pressure values. According to previous studies, it seems conceivable that maternal L-arginine treatment enters the fetal circulation by crossing the placenta. The lack of changes in FHR, however, suggests that no significant hemodynamic changes were induced by the treatment. Contrary to what happens in the mother, this may possibly be due to a low, if any, conversion of L-arginine to nitric oxide in the fetus.     

Changes in intrafollicular pressure in the rat ovary by nitric oxide and by alteration of systemic blood pressure

BACKGROUND: ovulation is associated with degradation of the follicular apex vasodilatation and increased permeability of ovarian vessels. These changes may maintain or increase intrafollicular pressure (IFP) at ovulation to cause rupture of the follicular wall. OBJECTIVE: to investigate the possible regulation of IFP during the ovulatory process. STUDY DESIGN: immature Sprague-Dawley rats were primed with pregnant mare serum gonadotrophin (PMSG; 10IU) and given hCG (10IU) 48h later. The ovary was exposed 48-60h after PMSG, micropipette inserted into the Graafian follicle and the IFP measured at three time periods: preovulatory (PO) 48h after PMSG; midovulatory (MO) 4-7h after hCG; late ovulatory (LO) 9-12h after hCG. The offset of the nitric oxide synthase (NOS) inhibitor L-arginine methyl ester (L-NAME), the alpha(1)-adrenoceptor agonist phenylephrine and the beta-adrenoceptor agonist isoprenaline were tested. RESULTS: phenylephrine given i.v. increased the systemic blood pressure, and significantly decreased the IFP in the LO phase (78% of pre-treatment value). Local administration of phenylephrine or isoprenaline (1ml of 1.5-15 microM) by superfusion over the ovary did not change the IFP. Local administration of L-NAME (1ml of 2 microM) significantly lowered (P<0.05) the IFP in the MO and LO phases, but was without effect in the PO phase. CONCLUSION: this study reveals that IFP regulation may be related to changes of the systemic blood pressure and that NO may be one local ovarian mediator in IFP regulation.     

Nitric oxide activity in women with intrauterine growth restriction treated by L-arginine

OBJECTIVES: The aim of the study was to find correlation between the nitric oxide metabolites such nitrite in healthy pregnant women and in intrauterine growth restriction. The decrease of nitric oxide metabolites production may be linked to endothelial cells deficiency. DESIGN: High risk of destruction of biological function of cells by free radical processes is observed in IUGR. It depends on NO deficiency and lipid peroxidation processes. Concentration of NO metabolites measured in pregnancy can show the correlation between oxidative stress and NO metabolism. MATERIAL AND METHODS: The study was undertaken in Medical University in Lodz in 2000-2002. The study group consisted of women with IUGR, the control one of healthy women. The group of IUGR was treated with L-arginine-nitric oxide precursor and acetylsalicylic acid. The nitrite activity was measured by Oxis kit, in Grees reaction and was expressed in mumol/l. RESULTS: In group of IUGR low concentration of NO metabolites was observed before treatment. After 20 days of treatment the concentration decreased. In the control group the value was higher than IUGR group/significant difference/and after 20 days of observation decreased as well. CONCLUSIONS: We found the difference between the two groups and the decrease of NO metabolite concentration in the course of pregnancy.     

Iron status parameters in preeclamptic women

Background  

Evidence of increased oxidative stress due to endothelial dysfunction in preeclampsia has been well established. Increase in the oxidative stress is catalyzed in the presence of free transitional metals. Therefore, the relationship of iron status with preeclampsia was under investigation.     

Coagulation inhibitors in preeclamptic pregnant women

Objective Our objective was to detect clinical evaluation of coagulation inhibitors in preeclamptic and normotensive pregnant women and to determine their important role in pathogenesis of preeclampsia.Methods A total of 20 mild, 20 severe preeclamptic and 45 normotensive pregnant women were included in this study. The plasma value of antithrombin III (AT-III) activity, proteins C and S activity, PT, PTT, fibrinogen and platelet counts were determined.Results The values AT-III were lower in women with severe preeclampsia than in controls (p<0.05). In all groups, there was no significantly difference in the concentration of protein C activity, protein S and fibrinogen (p>0.05). The plasma thrombocyte counts were significantly lower in severe preeclamptic women than in normotensive women (p<0.05). There was no significant difference in the prothrombin time value in all groups, but a significantly difference with regard to partial thromboplastin time between severe preeclamptic and the control group (p<0.0001). It was longer than the control.Conclusion The markers of hemostasis activation such as protein S, protein C activity together with fibrinogen levels are not useful tools but the reduction of AT-III and platelet counts would seem useful in different pathological situations in pregnancy to predict and monitor the severity of the condition.