L-arginine erythrocyte transport increases during pregnancy and immediately postpartum

OBJECTIVE: This study was undertaken to evaluate erythrocyte membrane transport of L-arginine in pregnancy and immediately postpartum. STUDY DESIGN: The study comprised 103 women with normal pregnancy, initially evaluated at the second trimester (II), followed into the third trimester (III), and immediately postpartum (PP). Total erythrocyte L-arginine uptake was measured with (14)C-L-arginine, at 37 degrees C, for 3 minutes. The maximal transport capacity (V(max)) and half-saturation constant (K(m)) were obtained with the use of Michaelis-Menten kinetics. Results are expressed as mean+/-SD. Analysis of variance, followed by Tukey test, was used in statistical analysis (alpha< or =.05). RESULTS: V(max) (micromol/L cells per hour) progressively increased at each consecutive time period: 779+/-283, 946+/-289, and 1349+/-390, at II, III, and PP, respectively (P<.001). Similarly, K(m) (micromol/L) values increased from 56+/-20 at time II, to 62+/-18 at time III, and 69+/-24 at PP (P<.001). CONCLUSION: Total erythrocyte L-arginine uptake (V(max) and K(m)) increases progressively along normal pregnancy, with a further increase immediately postpartum.     

Cerebrospinal fluid nitric oxide level changes in preeclampsia

OBJECTIVE: The purpose of this study was to determine the level of nitric oxide (NO) metabolites, nitrite and nitrate in human cerebrospinal fluid (CSF) and serum and to assess whether there is any relationship among CSF, serum nitrate-nitrite levels and preeclampsia. STUDY DESIGN: Twenty-one preeclamptic and 27 healthy pregnant women as control group who underwent cesarean section (C/S) were included in the study. Before administering local anesthetic for spinal anesthesia, 2 ml CSF and 4 ml venous blood sample were taken. CSF and serum total nitrite, direct nitrite and nitrate levels were determined spectrophotometrically. RESULTS: CSF total nitrite, direct nitrite and nitrate levels were significantly different between the two groups (21.00+/-1.68, 8.28+/-0.89 and 12.71+/-1.08 micromol/l, respectively versus 15.53+/-1.49, 5.57+/-0.39 and 9.96+/-1.45 micromol/l, respectively, P<0.05). Significantly higher serum nitrate level was found (31.84+/-2.31 micromol/l) in the control group compared to the preeclamptic group serum nitrate level (25.06+/-2.02 micromol/l). Statistical comparisons were performed by the Mann-Whitney U-test. CONCLUSION: CSF-NO is significantly higher but serum NO is lower in preeclamptic group compared with control group may suggest independent regulation of NO in the two compartments. The determination of CSF-NO metabolites could be useful to clarify whether increased NO production is predominantly associated with poor perfusion of the brain in preeclampsia.     

Measurement of the total antioxidant response in preeclampsia with a novel automated method

OBJECTIVES: Preeclampsia is one of the most serious complications of pregnancy. Free radical damage has been implicated in the pathophysiology of this condition. In this study, we aimed to measure the antioxidant capacity in plasma samples from normotensive and preeclamptic pregnant women to evaluate their antioxidant status using a more recently developed automated measurement method. STUDY DESIGN: Our study group contained 42 women, 24 of whom had preeclampsia, while 18 had normotensive pregnancies. We measured the total plasma antioxidant capacity for all patients, as well as the levels of four major individual plasma antioxidant components; albumin, uric acid, ascorbic acid and bilirubin, and as a reciprocal measure, their total plasma peroxide levels. RESULTS: Statistically significant differences (determined using Student's t-test) were noted between the normotensive and the preeclamptic groups for their total antioxidant responses and their vitamin C levels (1.31 +/- 0.12 mmol versus 1.06 +/- 0.41 mmol Trolox eq./L; 30.2 +/- 17.83 micromol/L versus 18.1 +/- 11.37 micromol/L, respectively), which were both considerably reduced in the preeclamptic patients. In contrast, the total plasma peroxide levels were significantly elevated in this group (49.8 +/- 14.3 micromol/L versus 38.8 +/- 9.6 micromol/L). CONCLUSIONS: We found a decreased total antioxidant response in preeclamptic patients using a simple, rapid and reliable automated colorimetric assay, which may suitable for use in any routine clinical biochemistry laboratory, and considerably facilitates the assessment of this useful clinical parameter. We suggest that this novel method may be used as a routine test to evaluate and follow up of the levels of oxidative stress in preeclampsia.     

Maternal serum nitric oxide levels associated with biochemical and clinical parameters in hypertension in pregnancy

OBJECTIVES: To measure maternal serum concentrations of total nitrites, as an index of nitric oxide synthesis, in normal and hypertensive pregnant women, and to examine the correlation between these concentrations and several variables of clinical interest. STUDY DESIGN: A total of 60 women in four different groups were studied: 10 normotensive pregnant women, 17 pregnant women with preeclampsia, 18 pregnant women with gestational hypertension and 15 pregnant women with chronic hypertension. Serum nitrite levels were determined using the Griess reaction after reduction with nitrate reductase. RESULTS: Serum nitrite levels were higher in preeclamptic women (34.11+/-14 micromol/l, P=0.04), lower in chronic hypertensive women (19.56+/-6.46 micromol/l, P=0.04) and similar in women with gestational hypertension (26.97+/-9.44 micromol/l) in comparison to the control group (25.37+/-7.24 micromol/l). Serum nitrite levels in preeclamptic women had significant positive correlations with hematocrit, fasting insulinemia, and apolipoprotein B and negative correlations with platelet count, serum phosphorus and glucose:insulin ratio. In pregnant women with chronic hypertension a negative correlation was found between serum nitrite levels and active partial thromboplastin time. In pregnant women with gestational hypertension, serum nitrite levels had negative correlations with birthweight and 24-h urine calcium, and positive correlations with mean corspuscular hemoglobin, 24-h urine sodium and maternal age. CONCLUSIONS: We suggest that in women with preeclampsia, a higher maternal nitric oxide level may act as a compensatory mechanism against hemoconcentration and platelet aggregation and that nitric oxide production may be related to some metabolic events. In women with gestational hypertension, higher serum nitrite levels may be related to clinical and biochemical findings common in preeclampsia. In chronic hypertension, a lower maternal nitric oxide level is related to the status of coagulation.     

Estimation of oxidative products of nitric oxide (nitrates, nitrites) in preeclampsia

Oxidative products of nitric oxide, serum nitrates and nitrites were estimated in 50 primigravidas with preeclampsia and in 50 gestation and age-matched normotensive primigravidas. Thirty three (66%) of these women had mild preeclampsia and 17 (34%) had severe preeclampsia. Serum nitrate and nitrite levels were significantly higher in preeclamptic women (nitrates - 15 +/- 1.17; nitrites - 11.82 +/- 1.16 micromol/L) than in the normotensive pregnant women (nitrates 11.82 +/- 1.16; nitrites - 5.08 +/- 0.47 micromol/L, p < 0.001). In preeclamptic women, serum nitrate and nitrite levels correlated with the severity of the disease (mild preeclampsia nitrate - 14.46 +/- 1.98; nitrite 6.21 +/- 0.84 micromol/L, severe preeclampsia nitrate - 16.65 +/- 3.64; Nitrite - 6.87 +/- 1.56 micromol/L). In preeclampsia there was significant positive correlation between nitrate and nitrite levels and diastolic blood pressure and proteinuria.     

妊娠高血压综合征患者血浆对体外培养的内皮细胞合成血管活 …

目的 探讨妊娠高血压综合征（妊高征）患者的血浆对体外培养的内皮细胞合成血管活性物质的影响,和妊高征患者血浆中是否存在某些引起内皮细胞损伤的物质。方法 应用放射免疫法测定２０例先兆子痫患者（先兆子痫组）及１５例正常晚期妊娠妇女（正常晚孕组）产前血浆前列环素（ＰＧＩ２）代谢产物６－ｋｅｔｏ－ＰＧＦ１α、血栓素（ＴＸＡ２）代谢产物ＴＸＢ２的水平。在体外培养的爬刮动脉内皮细胞中分别加入先兆子痫患者和正常晚     

Reduced L-arginine level and decreased placental eNOS activity in preeclampsia

Nitric oxide is produced enzymatically by the nitric oxide synthase (NOS), which converts L-arginine in the presence of oxygen to L-citrulline and NO. Moreover, it has been reported that asymmetric dimethylarginine (ADMA) acts as is an endogenous inhibitor of endothelial NOS (eNOS) by competing with the enzyme for L-arginine. In this study, we measured L-arginine and ADMA in normal and preeclamptic women, and also investigated the association between the Glu298Asp eNOS gene polymorphism and preeclampsia. Finally, we assessed eNOS expression levels in the placentas of both normal and preeclamptic patients, using Western blot and immunohistochemistry. L-arginine levels were found to be significantly lower in the preeclamptic women than in the normal pregnant women (p=0.02) but there were no significant differences in ADMA levels between the normal and preeclamptic women. We also determined there to be no association between the Glu298Asp eNOS gene and preeclampsia. With regard to placental eNOS expression, we detected a lower degree of eNOS expression in the preeclamptic syncytiotrophoblasts than in the normal syncytiotrophoblasts. We suggest that reduced L-arginine levels, rather than increased ADMA levels, contribute to the development of preeclampsia, and also that decreased placental eNOS expression constitutes a characteristic finding in preeclamptic placentas.     

Embryonic Production of Nitric Oxide and Its Role in Implantation: A Pilot Study

PURPOSE: To investigate the ability of human embryos to produce nitric oxide (NO) and correlate its production with embryo quality and pregnancy rate. METHODS: Twenty-three women participated in the study and were submitted to controlled ovarian stimulation and intracytoplasmic sperm injection. Embryos were singularly cultured in medium microdrops of 50 microL and were replaced, by transcervical transfer, at the 2- to 6-cell stage. In the culture media of each embryo the NO production was assessed by monitoring the levels of its stable oxidation products (nitrites/nitrates). RESULTS: All the 23 patients underwent embryo transfer. After microinjection 64 embryos were obtained. The mean number of transferred embryos was 2.61 +/- 0.46 and the pregnancy rate was 26%. The mean nitrite/nitrate concentrations of culture medium of each embryo was significantly higher (5.88 +/- 2.34 micromol/L) than in pure P-1 medium (0.81 +/- 0.21 micromol/L; p < 0.001) demonstrating an embryonic secretion of NO. Comparing pregnant (7.34 +/- 2.72 micromol/L) versus nonpregnant patients (5.53 +/- 1.49 micromol/L; p = 0.022), the mean nitrite/nitrate concentrations were significantly higher. Furthermore, the best quality embryos of pregnant women produced significantly higher nitrite/nitrate concentrations than those of not pregnant patients. CONCLUSIONS: It seems that NO production in nidating embryos is increased and that it may be primarily associated with a better morphology and a better growth potential of developing embryos.     

妊娠高血压疾病患者血浆细胞纤维结合蛋白水平变化的研究

检测各种妊娠高血压疾病患者的血浆细胞纤维结合蛋白（ｃＦＮ）水平变化,以探讨血浆ｃＦＮ在妊娠高血压疾病中的诊断价值。方法７３例妊娠高血压疾病患者按照国际高血压工作报告中的妊娠高血疾病分类方法,分为４个组：（１）暂时性高血压组１５例;（２）妊娠高血压综合征（妊高征）组３８例;（３）慢性高血压组１０例;（４）慢性高血压伴妊征组１０例。另选正常妊娠妇女３９例作为正常妊娠。采用酶联免疫吸附法检测上述５组患者     

Relation between serum uric acid and plasma adenosine levels in women with preeclampsia

The aim of this study was to examine the relationship between plasma adenosine and serum uric acid levels in women with preeclampsia. Maternal arterial blood sampling was performed to measure serum uric acid and plasma adenosine levels in 20 pregnant women complicated by preeclampsia and 22 normal pregnant women at 33-38 weeks of gestation. The average plasma adenosine levels were 0.31 +/- 0.12 micromol/l in the normal pregnant group and 0.45 +/- 0.11 micromol/l in the preeclampsia group. The mean serum uric acid level in women with preeclampsia was 5.9 +/- 0.60 mg/dl, significantly higher than in the normal pregnant women (4.4 +/- 0.69 mg/dl). Positive correlations were found between serum uric acid and plasma adenosine levels in both the group with (r(2) = 0.38, p < 0.05) and the group without (r(2) = 0.54, p < 0.05) preeclampsia. There was also a significant correlation between serum uric acid and plasma adenosine levels on the whole (r(2) = 0.59, p < 0.05). Our results suggest that increased adenosine is a contributing source of preeclamptic hyperuricemia.     

Increased vascular endothelial cell production of interleukin-6 in severe preeclampsia

OBJECTIVE: The purpose of this study was to determine whether plasma from women with severe preeclampsia stimulates the production of endothelial cell interleukin-6 production and whether vitamin E could inhibit this process. STUDY DESIGN: Human umbilical vein endothelial cells were cultured in the presence of 5% plasma from women with severe preeclampsia (n = 12) or healthy pregnant women at term (n = 12), with or without 50 micromol/L vitamin E. Levels of interleukin-6 in plasma and human umbilical vein endothelial cell-conditioned media were measured by enzyme-linked immunosorbent assay. RESULTS: Interleukin-6 levels were elevated 5-fold in preeclamptic plasma compared with normal pregnant plasma (P <.05). Human umbilical vein endothelial cell interleukin-6 production was increased 25% by preeclamptic plasma compared with normal pregnant plasma (P <.005), and increased interleukin-6 production by preeclamptic plasma was inhibited by vitamin E. CONCLUSION: Endothelial cell activation by preeclamptic plasma stimulates interleukin-6 production, which is inhibited by vitamin E. These findings provide a potential cellular mechanism for the beneficial effects of antioxidant therapy in preeclampsia.     

胎儿宫内生长迟缓孕妇静脉血及其新生儿脐血一氧化氮水平测定的临床意义

】     

Increased serum phosphodiesterase activity in women with pre-eclampsia

OBJECTIVE: To measure the activity of serum phosphodiesterase (PDE) in pre-eclampsia. DESIGN: Case-control study. SETTING: Nephrology Laboratory and Obstetrics Unit at S?o Lucas Hospital from Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil. SAMPLE: Twenty-nine normal and 28 pregnant women with pre-eclampsia. METHODS: Serum was collected from women with pre-eclampsia, at the time of diagnosis, and from gestation-matched controls. Circulating PDE activity was assessed by measuring consumption of the substrate thymidine 5'-monophosphate p-nitrophenyl ester and expressed as PDE units/l. MAIN OUTCOME MEASURES: Serum PDE Activity. RESULTS: Mean substrate consumption was higher in pre-eclamptic condition (V(max)= 15.8 +/- 1.4 versus 12.7 +/- 0.9 U/L, P= 3.7 x 10(-14)). CONCLUSION: These data suggest that altered PDE activity may play a role in pre-eclampsia endothelial dysfunction.     

正常妊娠及妊高征患者静脉血及新生儿脐血一氧化氮含量的测…

探讨一氧化氮含量与妊娠及妊高征的关系。方法,采用硝酸根还原酶与Ｇｒｉｅｓｓ反应相结合的方法,对４０例妊高征患者、４０例正常晚期妊娠妇女、２０例非孕妇女静脉血及妊高征组和晚孕组各２８例新生儿脐血中的ＮＯ代谢产物亚硝酸基／硝酸基进行测定。     

Vasorelaxant effect of levcromakalim on isolated umbilical arteries of preeclamptic women

OBJECTIVE: Potassium channel openers are revealed to be a new type of antihypertensive drug. We aimed to clarify the effects of levcromakalim, an ATP-sensitive potassium channel opener, on human isolated umbilical artery (UA) and to compare them with those of nifedipine and magnesium sulphate, which are currently used in the treatment of preeclampsia (PE). STUDY DESIGN: A total of 52 umbilical arteries, isolated immediately after delivery from 27 healthy and 25 preeclamptic pregnant women, were placed into 10-ml organ baths filled with Kreb's solution at physiological pH and temperature. The concentration-dependent relaxations in response to levcromakalim, nifedipine and magnesium sulphate were compared in vessels precontracted with serotonin (1 micromol/l). RESULTS: The maximal relative relaxation responses (E(max), expressed as percentage of serotonin-induced precontraction) to magnesium sulphate, nifedipine and levcromakalim in umbilical arteries were identical in the healthy (85.06+/-3.31, 84.80+/-3.01 and 80.37+/-5.32%, respectively) and preeclamptic (77.20+/-5.30, 83.36+/-2.37 and 79.13+/-4.30%, respectively) groups. CONCLUSION: Levcromakalim has a vasodilatory effect on the umbilical artery like magnesium sulphate and nifedipine, and serves as an antihypertensive potential that might be used in the treatment of preeclampsia. However, further experimental and clinical studies are needed to propose that ATP-sensitive potassium channel openers are beneficial drugs in cases of clinical preeclampsia.     

Endothelial dysfunction in preeclampsia. Increased homocysteine and decreased nitric oxide levels

Endothelial dysfunction underlies the pathogenesis of preeclampsia, but its mechanism has not yet been completely understood. Elevated oxygen free radicals may partially explain the endothelial cell damage. In this study, we have aimed to measure homocysteine (Hcy) and nitric oxide (NO) levels as endothelial dysfunction markers in preeclamptic women. Nineteen preeclamptic (33.9 +/- 1.4 weeks) and 15 gestational-age-matched normal pregnant women (35.5 +/- 0.7 weeks) were included in the study. Mean NO level was significantly lower (p < 0.001) and mean Hcy level was significantly higher (p < 0.001) in the preeclamptic group. Elevated Hcy and oxygen free radical levels could decrease NO levels due to the reaction with each other and reduced NO may increase blood pressure and ischemia in preeclamptic patients. We have concluded that increased Hcy and oxygen free radical levels, and decreased NO levels are closely associated with preeclampsia-related endothelial dysfunction.     

Relation between adenosine and T-helper 1/T-helper 2 imbalance in women with preeclampsia

OBJECTIVE: To evaluate the relationship between changes in plasma adenosine concentration and imbalances in the T-helper 1/T-helper 2 ratio in peripheral blood of women with preeclampsia. METHODS: Plasma adenosine concentrations and the T-helper 1/T-helper 2 ratio were examined in the peripheral blood of 16 preeclamptic and normal pregnant women. The proportion of specific T-cell marker CD4-positive cells expressing intracellular cytokines, interferon-gamma derived from T-helper 1 and interleukin-4 derived from T-helper 2 cells, were analyzed by flow cytometry. The ratio of interferon-gamma secreting cells to interleukin-4 secreting cells was taken as the T-helper 1/T-helper 2 ratio in vivo. The effect of the adenosine-receptor blocker 8-sulfophenyltheophylline was also measured in vitro. RESULTS: Mean plasma adenosine concentration in preeclampsia was significantly higher than that in normal pregnancy (0.68 +/- 0.07 micromol/L versus 0.39 +/- 0.06 micromol/L, P <.05). The proportions of interferon-gamma secreting cells increased and interleukin-4 secreting cells decreased significantly in preeclampsia, and the T-helper 1/T-helper 2 ratio in preeclampsia was significantly higher than in normal pregnancy (18.1 +/- 2.6 versus 9.9 +/- 1.5, P <.05). The increase of the proportion of interferon-gamma secreting cells after adenosine receptor blockade in preeclampsia significantly exceeded that of normal pregnancy. The T-helper 1/T-helper 2 ratio in preeclampsia was significantly greater than that in normal pregnancy (36% versus 17%, P <.05). CONCLUSION: Increased plasma adenosine may be involved in the regulation of imbalances in the T-helper 1/T-helper 2 ratio in women with preeclampsia.     

L-arginine infusion reduces blood pressure in preeclamptic women through nitric oxide release.

OBJECTIVE: This study investigates the biochemical and cardiovascular effects of L-arginine administration in normotensive pregnant women and women with preeclampsia. METHODS: The study groups consisted of 12 women with uncomplicated pregnancies and 17 preeclamptic patients, four of whom were on antihypertensive treatment. In both groups, saline infusion was started, followed by 30 g L-arginine administration, and finally more saline. Blood pressure was recorded every 5 minutes and blood samples were collected for measurement of serum citrulline, arginine, and nitrite levels. Amino acid assays were done by using high-performance liquid chromatography with fluorometric detection. RESULTS: L-Arginine infusion was associated with a significant reduction of blood pressure in both groups, the decrease being greater in the women with preeclampsia. Baseline serum citrulline and arginine levels were not significantly different between the two groups. L-Citrulline levels were significantly increased during infusion of L-arginine, and the increase was significantly lower in the women with preeclampsia. Serum nitrite levels were increased only in controls and not in preeclampsia patients. The total citrulline production stimulated by L-arginine was related inversely to baseline blood pressure values and was unrelated to clinical parameters such as gestational age at delivery, birth weight, and Apgar score. CONCLUSIONS: L-Arginine load in pregnant women is associated with increased nitric oxide (NO) production and hypotension. Despite a reduced ability to produce NO, patients with preeclampsia may benefit from L-arginine supplementation. Overall, these findings partially support the hypothesis that preeclampsia is characterized by a dysfunction of the L-arginine-NO pathway.     

Neurokinin B peptide serum levels are higher in normotensive pregnant women than in preeclamptic pregnant women

OBJECTIVES: The purpose of this study was to examine neurokinin B levels in serum from preeclamptic and normotensive and to investigate the role of neurokinin B in preeclampsia. STUDY DESIGN: Peripheral and uterine venous blood neurokinin B levels were measured in 14 normotensive and 8 preeclamptic pregnant women by radioimmunoassay. RESULTS: Neurokinin B levels in normotensive women were 4.91 +/- 2.67 nmol/L in peripheral and 5.59 +/- 2.06 nmol/L in uterine blood. In pregnant women with preeclampsia, neurokinin B levels were 2.79 +/- 1.68 nmol/L and 3.20 +/- 1.55 nmol/L, respectively. Neurokinin B levels were significantly higher in normotensive women (P=.032 in peripheral and P=.006 in uterine blood). CONCLUSIONS: Neurokinin B serum levels were higher in normotensive women. Higher neurokinin B concentrations in normotensive pregnant women may be due to the advanced gestational age and/or the result of a negative interaction of other vasoactive substances. The role of neurokinin B in preeclampsia remains to be determined.