Renal prostacyclin and thromboxane in normotensive and preeclamptic pregnant women and their infants

Regulation of vascular angiotensin II type 1 and type 2 receptor and angiotensin-(1-7)/MasR signaling in normal and hypertensive pregnancy

Normal pregnancy (Norm-Preg) is associated with a slight reduction in blood pressure (BP) and decreased BP response to vasoconstrictor stimuli such as angiotensin II (Ang II), although the renin-angiotensin-aldosterone system (RAAS) is upregulated. Preeclampsia (PE) is a complication of pregnancy manifested as hypertension-in-pregnancy (HTN-Preg), and dysregulation of angiotensin biosynthesis and signaling have been implicated. Ang II activates vascular Ang II type-1 receptor (AT1R) and Ang II type-2 receptor (AT2R), while angiotensin-(1-7) promotes Ang-(1-7)/MasR signaling. The role of AT1R in vasoconstriction and the activated cellular mechanisms are well-characterized. The sensitivity of vascular AT1R to Ang II and consequent activation of vasoconstrictor mechanisms decrease during Norm-Preg, but dramatically increase in HTN-Preg. Placental ischemia in late pregnancy could also initiate the release of AT1R agonistic autoantibodies (AT1AA) with significant impact on endothelial dysfunction and activation of contraction pathways in vascular smooth muscle including [Ca2+]c and protein kinase C. On the other hand, the role of AT2R and Ang-(1-7)/MasR in vascular relaxation, particularly during Norm-Preg and PE, is less clear. During Norm-Preg, increases in the expression/activity of vascular AT2R and Ang-(1-7)/MasR promote the production of endothelium-derived relaxing factors such as nitric oxide (NO), prostacyclin and endothelium-derived hyperpolarizing factor leading to generalized vasodilation. Aortic segments of Preg rats show prominent endothelial AT2R staining and increased relaxation and NO production in response to AT2R agonist CGP42112A, and treatment with AT2R antagonist PD123319 enhances phenylephrine-induced contraction. Decreased vascular AT2R and Ang-(1-7)/MasR expression and receptor-mediated mechanisms of vascular relaxation have been suggested in HTN-Preg animal models, but their role in human PE needs further testing. Changes in angiotensin-converting enzyme-2 (ACE2) have been observed in COVID-19 patients, and whether ACE2 influences the course of COVID-19 viral infection/immunity in Norm-Preg and PE is an intriguing area for research.

Adaptive regulation of endothelin receptor type-A and type-B in vascular smooth muscle cells during pregnancy in rats

Normal pregnancy is associated with systemic vasodilation and decreased vascular contraction, partly due to increased release of endothelium-derived vasodilator substances. Endothelin-1 (ET-1) is an endothelium-derived vasoconstrictor acting via endothelin receptor type A (ETA R) and possibly type B (ETB R) in vascular smooth muscle cells (VSMCs), with additional vasodilator effects via endothelial ETB R. However, the role of ET-1 receptor subtypes in the regulation of vascular function during pregnancy is unclear. We investigated whether the decreased vascular contraction during pregnancy reflects changes in the expression/activity of ETAR and ETBR. Contraction was measured in single aortic VSMCs isolated from virgin, mid-pregnant (mid-Preg, day 12), and late-Preg (day 19) Sprague-Dawley rats, and the mRNA expression, protein amount, tissue and cellular distribution of ETAR and ETBR were examined using RT-PCR, Western blots, immunohistochemistry, and immunofluorescence. Phenylephrine (Phe, 10(-5)  M), KCl (51 mM), and ET-1 (10(-6)  M) caused VSMC contraction that was in late-Preg < mid-Preg and virgin rats. In VSMCs treated with ETB R antagonist BQ788, ET-1 caused significant contraction that was still in late-Preg < mid-Preg and virgin rats. In VSMCs treated with the ETAR antagonist BQ123, ET-1 caused a small contraction; and the ETBR agonists IRL-1620 and sarafotoxin 6c (S6c) caused similar contraction that was in late-Preg < mid-Preg and virgin rats. RT-PCR revealed similar ETAR, but greater ETBR mRNA expression in pregnant versus virgin rats. Western blots revealed similar ETAR, and greater protein amount of ETBR in endothelium-intact vessels, but reduced ETBR in endothelium-denuded vessels of pregnant versus virgin rats. Immunohistochemistry revealed prominent ETBR staining in the intima, but reduced ETAR and ETBR in the aortic media of pregnant rats. Immunofluorescence signal for ETAR and ETBR was less in VSMCs of pregnant versus virgin rats. The pregnancy-associated decrease in ETAR- and ETBR-mediated VSMC contraction appears to involve downregulation of ETAR and ETBR expression/activity in VSM, and may play a role in the adaptive vasodilation during pregnancy.

Challenges posed to the maternal circulation by pregnancy

In primates, adequate growth of the fetus depends on the development of the uteroplacental unit. On the fetal side, this is achieved by the creation of the vascular network of the placenta. On the maternal side, the transformation of the spiral arteries into saccular nonreactive vessels by the trophoblast provides high blood flow to the intervillous space. Apart from the changes in the uterine arteries, the mother expands her plasma volume – at the expense of stimulating the renin-angiotensin-aldosterone system – and her cardiac output. In the maintaining of normotension in the face of an increased cardiac output and plasma volume, the renin-angiotensin-aldosterone system requires an enhanced vasodilator synthesis. Finally, in the late stages of pregnancy, a normal endothelial function is required to provide an ample margin to the activation provoked by deportation of syncytiotrophoblast fragments/factors to the maternal circulation. These four adaptative processes require various interrelated vasodilator systems. Deficient adaptations cause isolated or proteinuric arterial hypertension, intrauterine growth restriction, preterm delivery, and stillbirths, among others. Moreover, a normal or a defective adaptation to pregnancy influences maternal cardiovascular health in later life, as evidenced by various studies, most of them epidemiological; thus, pregnancy is now considered a stress test to the maternal cardiovascular system. Because of this, women planning to become pregnant should be screened for clinical and biochemical cardiovascular risks. Inversely, women presenting with hypertension in pregnancy should be thoroughly studied to detect and correct cardiovascular risks. The incorporation of the predictive value of a hypertensive pregnancy should help reduce cardiovascular disease in women.

Vasodilator factors in the systemic and local adaptations to pregnancy

We postulate that an orchestrated network composed of various vasodilatory systems participates in the systemic and local hemodynamic adaptations in pregnancy. The temporal patterns of increase in the circulating and urinary levels of five vasodilator factors/systems, prostacyclin, nitric oxide, kallikrein, angiotensin-(1-7) and VEGF, in normal pregnant women and animals, as well as the changes observed in preeclamptic pregnancies support their functional role in maintaining normotension by opposing the vasoconstrictor systems. In addition, the expression of these vasodilators in the different trophoblastic subtypes in various species supports their role in the transformation of the uterine arteries. Moreover, their expression in the fetal endothelium and in the syncytiotrophoblast in humans, rats and guinea-pigs, favour their participation in maintaining the uteroplacental circulation. The findings that sustain the functional associations of the various vasodilators, and their participation by endocrine, paracrine and autocrine regulation of the systemic and local vasoactive changes of pregnancy are abundant and compelling. However, further elucidation of the role of the various players is hampered by methodological problems. Among these difficulties is the complexity of the interactions between the different factors, the likelihood that experimental alterations induced in one system may be compensated by the other players of the network, and the possibility that data obtained by manipulating single factors in vitro or in animal studies may be difficult to translate to the human. In addition, the impossibility of sampling the uteroplacental interface along normal pregnancy precludes obtaining longitudinal profiles of the various players. Nevertheless, the possibility of improving maternal blood pressure regulation, trophoblast invasion and uteroplacental flow by enhancing vasodilation (e.g. L-arginine, NO donors, VEGF transfection) deserves unravelling the intricate association of vasoactive factors and the systemic and local adaptations to pregnancy.

Increased vascular angiotensin type 2 receptor expression and NOS-mediated mechanisms of vascular relaxation in pregnant rats

Normal pregnancy is associated with reduced blood pressure (BP) and decreased pressor response to vasoconstrictors, even though the renin-angiotensin system is upregulated. Angiotensin II (ANG II) activates both angiotensin type 1 receptors (AT(1)Rs) and angiotensin type 2 receptors (AT(2)Rs). Although the role of the AT(1)R in vascular contraction is well documented, the role of the AT(2)R in vascular relaxation, particularly during pregnancy, is less clear. It was hypothesized that the decreased BP and vasoconstriction during pregnancy was, at least in part, due to changes in AT(2)R amount, distribution, and/or postreceptor mechanisms of vascular relaxation. To test this hypothesis, systolic BP was measured in virgin and pregnant (day 19) Sprague-Dawley rats. Isometric contraction/relaxation was measured in isolated aortic rings, and nitric oxide (NO) production was measured using 4-amino-5-methylamino-2',7'-difluorescein fluorescence. AT(1)R and AT(2)R mRNA expression and protein amount were measured in tissue homogenates using real-time RT-PCR and Western blots, and their local distribution was visualized in cryosections using immunohistochemistry and immunofluorescence. BP was lower in pregnant than virgin rats. Phenylephrine (Phe) caused concentration-dependent contraction that was reduced in the aorta of pregnant compared with virgin rats. Treatment with the AT(2)R antagonist PD-123319 caused greater enhancement of Phe contraction, and the AT(2)R agonist CGP-42112A caused greater relaxation of Phe contraction in the aorta of pregnant than virgin rats. ANG II plus the AT(1)R blocker losartan induced greater NO production in the aorta of pregnant than virgin rats. RT-PCR revealed increased mRNA expression of vascular endothelial NO synthase (eNOS), little change in AT(1)Rs, and increased AT(2)Rs in pregnant compared with virgin rats. Western blots revealed an increased protein amount of activated phospho-eNOS, little change in AT(1)Rs, and increased AT(2)Rs in pregnant compared with virgin rats. Immunohistochemistry and immunofluorescence analysis in aortic sections of virgin rats revealed abundant AT(1)R staining in tunica media that largely colocalized with actin in vascular smooth muscle and less AT(2)Rs mainly in the tunica intima and endothelium. In pregnant rats, AT(1)R staining in the smooth muscle layer and adventitia was reduced, and endothelial AT(2)R staining was enhanced. These data suggest an enhanced AT(2)R-mediated vascular relaxation pathway involving increased expression/activity of endothelial AT(2)Rs and increased postreceptor activated phospho-eNOS, which may contribute to the decreased BP during pregnancy.

Preventing pregnancy-induced hypertension: are there regional differences for this global problem?

Developing countries have had persistently higher rates of maternal and child mortality due to pre-eclampsia in comparison with developed countries. Moreover, evidence from studies of interventions to prevent pre-eclampsia have given contradictory results. In this review, we discuss the underlying causes of pre-eclampsia, and the results of clinical trials performed to prevent this disease, that support the proposal that the causes and strategies to prevent pre-eclampsia are different in developed and developing countries. We also suggest that the establishment of an adequate prenatal care is the only effective way to reduce the incidence of pre-eclampsia in populations from developing countries, especially in women at high risk of pregnancy-induced hypertension.

Predicting pregnancy-induced hypertension with dynamic hemodynamics

AIM

To study dynamic changes in the hemodynamic parameters in pregnant women during different weeks of gestation and to comprehend changes to the cardiovascular system in normal pregnant women and in patients with pregnancy-induced hypertension (PIH), with the object of finding predictors of pregnancy-induced hypertension.

METHODS

Radialis artery pulse waves of 132 pregnant women were examined from 10 weeks of gestation onward, and the subjects' hemodynamics were examined every 4 weeks.

RESULTS

In the women with PIH hemodynamic changes occurred earlier than the onset of disease and even presented in early pregnancy; there might be another mode, and there were factors disturbing the blood pressure modulating mechanism.

CONCLUSION

The prediction of PIH from the dynamic changes in hemodynamic parameters has significant implications for clinical practice.

Prostacyclin/thromboxane early changes in pregnancies that are complicated by preeclampsia

OBJECTIVE

The purpose of this study was to examine 6-keto-prostaglandin F(1)(alpha) and thromboxane B(2) plasma levels throughout normotensive and preeclamptic pregnancies and to analyze the predictive values of these quantifications for the detection of preeclampsia during the second trimester of pregnancy.

STUDY DESIGN

Blood samples were collected from 30 healthy, nonpregnant women and at 4-week intervals from a cohort of nulliparous women who were recruited before 16 weeks of gestation. Preeclampsia developed in 26 patients; 52 normotensive control subjects were matched from the same cohort. The 6-keto-prostaglandin F(1)(alpha) and thromboxane B(2) were assayed by radioimmunoassay. Trends were compared between pregnancy groups and with the nonpregnant women. Predictive values were determined with the second-trimester assessments.

RESULTS

The 6-keto-prostaglandin F(1)(alpha)/thromboxane B(2) ratio decreased throughout pregnancy in women with preeclampsia; there were no significant changes in normotensive women. We found higher thromboxane B(2) levels within the group with preeclampsia during the first gestational trimester (preeclampsia, 188 +/- 17 pg/mL; control, 119 +/- 4.8 pg/mL [mean +/- SEM]; P =.001). During the third trimester, patients with preeclampsia had lower 6-keto-prostaglandin F(1)(alpha) levels than did control subjects (preeclampsia, 191 +/- 9.8 pg/mL; control, 288 +/- 10 pg/mL; P =.001). The 6-keto-prostaglandin F(1)(alpha)/thromboxane B(2) ratio was suitable to calculate predictive values; the best cutoff point and time interval were 3.0 and 22 to 26 weeks of gestation, respectively. Sensitivity, specificity, and positive and negative predictive values were 88%, 97%, 69%, and 99%, respectively; the odds ratio was 14.6 (95% CI, 6.9-30.4).

CONCLUSION

The prostacyclin/thromboxane ratio favored vasoconstriction early in gestation in women in whom preeclampsia developed. A 6-keto-prostaglandin F(1)(alpha)/thromboxane B(2) ratio of <or=3.0 at 22 to 26 weeks of gestation had a high predictive value for the development of preeclampsia.

Vascular mechanisms of increased arterial pressure in preeclampsia: lessons from animal models

Normal pregnancy is associated with reductions in total vascular resistance and arterial pressure possibly due to enhanced endothelium-dependent vascular relaxation and decreased vascular reactivity to vasoconstrictor agonists. These beneficial hemodynamic and vascular changes do not occur in women who develop preeclampsia; instead, severe increases in vascular resistance and arterial pressure are observed. Although preeclampsia represents a major cause of maternal and fetal morbidity and mortality, the vascular and cellular mechanisms underlying this disorder have not been clearly identified. Studies in hypertensive pregnant women and experimental animal models suggested that reduction in uteroplacental perfusion pressure and the ensuing placental ischemia/hypoxia during late pregnancy may trigger the release of placental factors that initiate a cascade of cellular and molecular events leading to endothelial and vascular smooth muscle cell dysfunction and thereby increased vascular resistance and arterial pressure. The reduction in uterine perfusion pressure and the ensuing placental ischemia are possibly caused by inadequate cytotrophoblast invasion of the uterine spiral arteries. Placental ischemia may promote the release of a variety of biologically active factors, including cytokines such as tumor necrosis factor-alpha and reactive oxygen species. Threshold increases in the plasma levels of placental factors may lead to endothelial cell dysfunction, alterations in the release of vasodilator substances such as nitric oxide (NO), prostacyclin (PGI(2)), and endothelium-derived hyperpolarizing factor, and thereby reductions of the NO-cGMP, PGI(2)-cAMP, and hyperpolarizing factor vascular relaxation pathways. The placental factors may also increase the release of or the vascular reactivity to endothelium-derived contracting factors such as endothelin, thromboxane, and ANG II. These contracting factors could increase intracellular Ca(2+) concentrations ([Ca(2+)](i)) and stimulate Ca(2+)-dependent contraction pathways in vascular smooth muscle. The contracting factors could also increase the activity of vascular protein kinases such as protein kinase C, leading to increased myofilament force sensitivity to [Ca(2+)](i) and enhancement of smooth muscle contraction. The decreased endothelium-dependent mechanisms of vascular relaxation and the enhanced mechanisms of vascular smooth muscle contraction represent plausible causes of the increased vascular resistance and arterial pressure associated with preeclampsia.

Urinary vasodilator and vasoconstrictor angiotensins during menstrual cycle, pregnancy, and lactation

Since normal human pregnancy is characterized by normotension in the face of an increased renin-angiotensin-aldosterone system (RAAS), we evaluated the temporal pattern of urinary excretion of a novel vasodilator within this system, angiotensin-(1-7) (Ang-[1-7]), during the menstrual cycle, pregnancy, and lactation. The urinary profiles of Ang I, Ang II, human chorionic gonadotropin, 17beta-estradiol, and progesterone were also determined. During the menstrual cycle, urinary Ang-(1-7) and Ang II remained stable (mean cycle value: 94.6 +/- 11.3 and 11.4 +/- 1.1 pmol/g of creatinine, respectively) in nine females. In 10 normal pregnant women, urinary Ang-(1-7) and Ang II increased throughout gestation, averaging 1499.8 +/- 310 and 224.4 +/- 58 pmol/g of creatinine, respectively (p < 0.05) at wk 35 and falling during lactation to 394.0 +/- 95 and 65.7 +/- 20 pmol/ g of creatinine (p < 0.05), respectively. The Ang-(1-7)/Ang II ratio was unchanged in the different reproductive periods. During the menstrual cycle, Ang II and Ang-(1-7) correlated with 17beta-estradiol and progesterone using multivariate analysis (r = 0.31, p < 0.001) and r = 0.28, p < 0.02, respectively). During gestation, 17beta-estradiol and progesterone correlated with urinary Ang-(1-7) (r = 0.48, p < 0.001 and r = 0.47, p < 0.001, respectively) and Ang II (r = 0.24, p < 0.03 and r = 0.25, p < 0.03, respectively); by multiple regression, only Ang-(1-7) correlated with both steroids (r = 0.49,p < 0.001). The progressive rise of Ang-(1-7) throughout gestation, probably modulated by estrogen and progesterone, suggests a physiologic counterregulation within the RAAS.

Urinary prostaglandin excretion in pregnancy: the effect of dietary sodium restriction

INTRODUCTION

Dietary sodium restriction results in activation of the renin-angiotensin-aldosterone-system. In the non-pregnant situation renin release in response to a low sodium diet is mediated by prostaglandins. We studied the effect of dietary sodium restriction on urinary prostaglandin metabolism in pregnancy.

PATIENTS AND METHODS

In a randomized, longitudinal study the excretion of urinary metabolites of prostacyclin (6-keto-PGF(1 alpha)and 2,3-dinor-6-keto-PGF(1 alpha)) and thromboxane A(2)(TxB(2)and 2,3-dinor-TxB(2)) was determined throughout pregnancy and post partum in 12 women on a low sodium diet and in 12 controls.

RESULTS

In pregnancy the excretion of all urinary prostaglandins is increased. The 6-keto-PGF(1 alpha)/ TxB(2)-ratio as well as the 2, 3-dinor-6-keto-PGF(1 alpha)/ 2,3-dinor-TxB(2)-ratio did not significantly change in pregnancy. CONCLUISION Prostacyclin and thromboxane do not seem to play an important role in sodium balance during pregnancy.

Umbilical cord serum levels of thromboxane B2 in term infants of women who participated in a placebo-controlled trial of low-dose aspirin

OBJECTIVE

Our aim was to quantify thromboxane B2 (TXB2) in umbilical cord serum of term infants of nulliparous, low-risk women who were randomly assigned to either placebo or low-dose (60 mg) aspirin (ASA) on a daily basis from 24 weeks' gestation through delivery as part of a randomized clinical trial for prevention of preeclampsia.

METHODS

Umbilical cord sera from 230 singleton, term infants whose mothers were involved in our low-dose ASA trial were assayed for TXB2, the stable metabolite of thromboxane A2, without knowledge of treatment or outcome data. The data were related to assigned treatment group, longitudinal pattern of maternal serum TXB2 levels, and other maternal and newborn characteristics. The data also were analyzed according to whether or not maternal serum levels of TXB2 at 29-31, 34-36, and delivery were reduced > or =50% compared to values prior to initiation of the trial.

RESULTS

Umbilical cord TXB2 levels (ng/ml, mean +/- SE) were significantly lower at term in the ASA group (36.1 +/- 3.3, n = 111) than in the placebo group (56.6 +/- 5.7, n = 119; P = 0.002). Umbilical cord TXB2 levels were correlated to those in maternal serum at delivery in the ASA group (r = 0.3441; P = 0.0005) but not in the placebo group (r = 0.0626; P = 0.53). Regardless of assigned treatment group, infants whose mothers had a > or =50% longitudinal reduction in serum TXB2 had lower umbilical cord TXB2 levels (39.2 +/- 3.6, n = 114) than infants whose mothers had <50% reductions in TXB2 (54.6 +/- 5.9, n = 116; P = 0.027). Birthweights of these infants correlated inversely (r = 0.1678, P = 0.017) with maternal serum TXB2 at delivery but not to umbilical cord TXB2 levels; the best correlation between birthweight and maternal serum TXB2 was noted in pregnancies assigned to receive placebo (r = -0.2558, P = 0.009).

CONCLUSIONS

Umbilical cord serum levels of TXB2 1) are reduced in instances of long-term maternal ingestion of ASA, 2) correlate well with maternal serum levels of TXB2 at delivery when there is evidence for consistent maternal use of ASA, but 3) do not correlate with maternal serum TXB2 levels when there is no evidence for frequent maternal ingestion of cyclooxygenase inhibitors. These data suggest that the capacity for platelet production of TXA2 in fetal and maternal compartments are regulated independently. Finally, there is an inverse relationship between maternal serum TXB2 levels at delivery and birthweight of newborn infants that is most evident among the pregnancies assigned to placebo and also among pregnancies in which there was little evidence to suggest a pattern of cyclooxygenase inhibitor use during pregnancy.

Pre-eclampsia does not change the adhesion molecule status in the placental bed

During normal placentation trophoblast cells invade maternal tissues and remodel the uterine arteries into low-resistance channels. In pre-eclampsia, trophoblast invasion is impaired and this, along with endothelial dysfunction, has been suggested to play a role in the pathogenesis of pre-eclampsia. We studied the expression of adhesion molecules important for leukocyte extravasation in the placental bed with immunohistochemistry and compared the expression in pre-eclampsia to that in normal pregnancy. Our major finding was that only invasive trophoblasts expressed cutaneous lymphocyte antigen-1 (CLA-1) in the third trimester of pregnancy, whereas villous trophoblasts did not. In the first trimester both villous trophoblasts and invasive trophoblast cells in decidua remained negative for CLA-1. Pre-eclampsia did not change the expression of leukocyte-endothelium adhesion or lymphocyte homing-associated antigens, ICAM-1, ICAM-2, VCAM, P-selectin, E-selectin, L-selectin, CLA-1, CD73, VAP-1 and alphaEbeta7 in the placental bed. Furthermore, pre-eclampsia was not associated with an aberrant accumulation of lymphocytes carrying antigens of any particular known organ-specific homing systems. The results on the unchanged pattern of adhesion molecule expression in pre-eclampsia suggests that there is no major change in the adhesive properties of the endothelium of the placental bed in pre-eclampsia.

Blood pressure and vasoactive hormones in mild preeclampsia and normal pregnancy

OBJECTIVE

Changes in vasoactive hormones are reported to play an important role in the pathogenesis of preeclampsia linking placental hypoperfusion with hypertension, systemic disease, and proteinuria. We, therefore, studied diurnal patterns of vasoactive hormones in mild preeclampsia.

METHODS

Venous blood samples were drawn every 2 h over 25 h for measurements of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), norepinephrine, renin activity, and aldosterone and two urine collections (12 h each) for stable prostaglandin metabolite measurements. The patients were nine women with mild preeclampsia and, for comparison, nine control women matched for gestation and parity.

RESULTS

Women with mild preeclampsia had higher norepinephrine levels throughout 25 h, and lower systemic prostacyclin production as measured by the urinary 2,3-dinor-6-keto PGF1 alpha excretion during the daytime. Plasma endothelin and ANP and BNP concentrations tended to be higher throughout 25 h in preeclampsia, but differences between the two groups did not reach levels of statistical significance. Plasma renin activity and aldosterone did not differ between the groups. Whereas control women exhibited a diurnal variation in plasma norepinephrine, ANP, BNP, and aldosterone, and in both urinary prostacyclin and thromboxane A2 metabolites, this was less distinct or absent in patients with mild preeclampsia.

CONCLUSIONS

We conclude that mild preeclampsia is associated with elevated plasma norepinephrine levels, lower systemic daytime production of prostacyclin, and blunting of the normal diurnal variation for a number of indices including plasma levels of BNP, ANP, norepinephrine, and aldosterone, and urinary prostacyclin metabolites.

An imbalance between prostacyclin and thromboxane in relation to cerebral blood flow in neonates with maternal preeclampsia

OBJECTIVE

A disturbance of prostacyclin (PGI2) and thromboxane A2 (TXA2) balance has been reported in preeclampsia. However, little is known about the concentrations of these prostanoids in neonates born to preeclamptic pregnant women. The purpose of this study is to determine whether the PGI2 and TXA2 concentrations are altered and whether the prostanoid balance correlates to the cerebral blood flow in neonates born to preeclampsia.

METHODS

Spontaneously voided urine samples were collected from 20 neonates of normotensive and 16 neonates of preeclamptic women during the first 24 h after birth. We measured by radioimmunoassay the concentrations of urinary 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha) and 11-dehydro-thromboxane B2 (11-dehydro-TXB2), respectively. Blood flow velocity in the middle cerebral artery was studied by pulsed Doppler ultrasonography in the neonates between 17 and 38 h after birth.

RESULTS

There was no significant difference between the urinary 6-keto-PGF1alpha in the neonates of mothers with and without preeclampsia (median, 5.3 vs. 3.6 ng/mg of creatinine). In contrast, the urinary 11-dehydro-TXB2 and the ratio of 11-dehydro-TXB2 to 6-keto-PGF1alpha in the neonates of mothers with preeclampsia were significantly lower as compared with the neonates without preeclampsia, respectively (13.7 vs. 20.6 ng/mg of creatinine and 3.0 vs. 5.2, median). The resistance index in the middle cerebral artery was significantly reduced in the neonates with preeclampsia than without preeclampsia (0.67 +/- 0.01 vs. 0.74 +/- 0.02, mean +/- SEM).

CONCLUSIONS

There was an association between maternal preeclampsia and the imbalance in the neonatal urinary excretion of PGI2 and TXA2 metabolites. This imbalance may contribute to the regulation of cerebral blood flow.

Involvement of thromboxane A2 and prostacyclin in the early pulmonary hypertension after porcine meconium aspiration

Severe perinatal aspiration of meconium is frequently complicated by unsuccessful neonatal adaptation with associated pulmonary hypertension. This vascular complication is supposedly related to pulmonary release of vasoconstrictory agents, including metabolites of arachidonic acid. Thus, to investigate the role of prostanoids on these meconium-induced circulatory changes in the lungs, the hemodynamic response to meconium instillation was studied in acetylsalicylic acid-pretreated juvenile pigs. Twelve 10-wk-old pigs with adapted lung circulation received 3 mL/kg of 65 mg/mL human meconium via the endotracheal tube. Six of them were medicated with 10 mg/kg acetylsalicylic acid 30 min before meconium insufflation. Hemodynamic parameters and urinary excretion of stable metabolites of thromboxane A2 and prostacyclin were measured serially for 6 h after the insult. Meconium administration induced a biphasic increase in mean pulmonary artery pressure and pulmonary vascular resistance, and a rapid rise in urinary levels of prostanoid metabolites. Acetylsalicylic acid pretreatment prevented the initial (0-1 h) pulmonary hypertensive response and increase in prostanoid excretion. During the second phase (1-6 h), acetylsalicylic acid did not attenuate the progressive increase in mean pulmonary artery pressure and pulmonary vascular resistance nor did it affect the longitudinal distribution of the pulmonary resistances. Our results thus show that in adapted porcine lungs, arachidonic acid metabolites contribute to the early hypertensive response, but have only minor effects during the second phase vascular hypertension.

The long-term effects of oral and transdermal postmenopausal hormone replacement therapy on nitric oxide, endothelin-1, prostacyclin, and thromboxane

OBJECTIVE

Oral postmenopausal hormone replacement therapy (HRT) decreases the risk of cardiovascular disorders, but the mechanisms of this protection are largely unknown. We compared the long-term effects of sequential oral HRT and transdermal HRT on vasodilatory nitric oxide and prostacyclin as well as vasoconstrictive endothelin- and thromboxane A2, all of which may be factors in the protective effect of HRT against cardiovascular disorders.

DESIGN

Prospective, randomized study.

SETTING

Department of Obstetrics and Gynecology at a university hospital.

PATIENT(S)

Fifty-two healthy postmenopausal female nonsmokers (n = 42) or smokers (n = 10) who had climacteric symptoms.

INTERVENTION(S)

The women received either oral HRT (2 mg of estradiol on days 1-12, 2 mg of estradiol plus 1 mg of norethisterone acetate on days 13-22, and 1 mg of estradiol on days 23-28; n = 21) or transdermal HRT (50 microg/d of estradiol on days 1-28 followed by 250 microg/d of norethisterone acetate on days 14-28; n = 21) for 1 year. Ten female smokers received transdermal HRT for 1 year.

MAIN OUTCOME MEASURE(S)

Plasma levels of nitrate as an index of nitric oxide production, endothelin-1, and urinary output of the prostacyclin metabolite (2,3-dinor-6-keto-PGF1alpha) and that of the thromboxane A2 metabolite (2,3-dinorthromboxane B2) were measured before and during the combined phases of the 2nd, 6th, and 12th treatment months.

RESULT(S)

Both regimens increased plasma estradiol levels and alleviated vasomotor symptoms. Neither regimen caused significant changes in nitrate, endothelin-1, prostacyclin, or thromboxane A2 in nonsmoking women. Female smokers had significantly higher levels of endothelin-1, which were significantly reduced by transdermal HRT at 6 months of treatment.

CONCLUSION(S)

Nitric oxide, endothelin-1, prostacyclin, and thromboxane A2 are not of primary importance in the protective effect of sequential oral HRT against cardiovascular disorders in otherwise healthy nonsmoking postmenopausal women. In this regard, transdermal HRT appears comparable to oral HRT. Postmenopausal female smokers have high levels of endothelin-1 that are reduced by transdermal HRT.

Do prostacyclin and thromboxane contribute to the "protective effect" of pregnancies with chronic hypertension? A preliminary prospective longitudinal study

OBJECTIVE

The aim of this study was to assess prospectively the urinary excretion of renal and systemic metabolites of thromboxane and prostacyclin in normotensive and chronic hypertensive pregnancies.

STUDY DESIGN

Pregnant hospital employees were invited to collect 24-hour urine samples weekly from the seventh week until delivery. Concentrations of renal metabolites (thromboxane B2, 6-keto-prostaglandin F1alpha) were measured by radioimmunoassay after extraction. Systemic metabolites (2,3-dinor-thromboxane B2, 2,3-dinor-6-keto-prostaglandin F1alpha) were assessed by enzyme immunoassay after extraction and high-pressure liquid chromatographic separation.

RESULTS

Thromboxane B2 excretion was similar in normotensive and hypertensive pregnancies, whereas a twofold increase of 6-keto-prostaglandin F1alpha was observed in hypertensive compared with normotensive pregnancies (7537 +/- 349 vs 3857 +/- 202 pg/mg creatinine, p < 0.001). During pregnancy in both conditions measurements displayed uniform excretion of thromboxane B2 with progressively increased levels of 6-keto-prostaglandin F1alpha in chronic hypertension (R2 = 0.60, p < 0.005). Mean excretion of 2,3-dinor-thromboxane B2 averaged 1208 +/- 65 and 898 +/- 48 pg/mg creatinine in normotensive and hypertensive pregnancies (p < 0.001), mainly due to significant decreased concentrations in hypertension in the first half of pregnancy. Conversely, 2,3-dinor-6-keto-prostaglandin F1alpha levels were 845 +/- 39 and 1226 +/- 67 pg/mg creatinine in normotensive and hypertensive pregnancies (p < 0.001), mostly because of significantly increased production in hypertension from 22 weeks onward. Ratios of both renal and systemic metabolites favored increased prostacyclin production in chronic hypertension.

CONCLUSION

In contrast to preeclampsia, uncomplicated mild to moderate chronic hypertensive pregnancies are characterized by an excess production of prostacyclin with unaltered or even lower thromboxane concentrations, which may contribute to the general favorable outcome of this hypertensive condition.

Effect of antiestrogen regimen on prostacyclin and thromboxane A2 in postmenopausal patients with breast cancer: evidence of significance of hypertension, smoking or previous use of estrogen therapy

To explore the mechanism(s) by which antiestrogens may protect against the development of cardiovascular disorders, we measured the production of vasodilatory, antiaggregatory prostacyclin (PGI2) and that of vasoconstrictive, proaggregatory thromboxane A2 (TxA2) before and after 6 months' use of antiestrogens in postmenopausal patients after operation for stage II breast cancer (n = 38). Urine samples were assayed by high performance liquid chromatography and radio-immunoassays for 2,3-dinor-6-ketoprostaglandin F1 alpha (= metabolite of PGI2, dinor-6-keto) and for 2,3-dinor-thromboxane B2 (= metabolite of TxA2, dinor-TxB2). In addition, in 35 of these 38 patients we assayed the capacity of platelets to produce thromboxane A2 during standardized blood clotting. The 4 patients using low-dose aspirin had low thromboxane production, and were excluded from further analysis of the data. An antiestrogen regimen consisting either of tamoxifen (n = 15) or of toremifene (n = 19) caused no changes in production of PGI2 or TxA2, or in their ratio, and in this regard, these antiestrogens behaved similarly. Hypertensive patients (n = 7) using different anti-hypertensive agents were characterized by reduced urinary out-put of dinor-6-keto (18.5 +/- 6.1 vs 35.5 +/- 18.5 ng/mmol, mean +/- SD, p < 0.05) and reduced platelet capacity to produce TxA2 (62.6 +/- 67.8 vs 134.6 +/- 75.6 ng/mL, p < 0.05). The patients (n = 15) who had used estrogen replacement therapy (ERT) up until diagnosis of breast cancer showed reduced dinor-TxB2 excretion (15.5 +/- 12.7 vs 29.9 +/- 20.9 ng/mmol, p < 0.05) before initiation of antiestrogens, and elevated dinor-6-keto output during the antiestrogen regimen (32.4 +/- 21.2 vs 22.7 +/- 8.7 ng/mmol, p = 0.07). Smokers (n = 6) had elevated dinor-TxB2 output before and during antiestrogen use. Thus we conclude that the cardiovascular protection provided by an antiestrogen regimen is unlikely to be mediated through vaso- and platelet active PGI2 and TxA2.

Development of an enzyme-linked immunosorbent assay for 2,3-dinor-6-keto-prostaglandin F1 alpha in urine using a monoclonal antibody

OBJECTIVES

To develop and validate an enzyme-linked immunosorbent assay (ELISA) for measurement of urinary 2,3-dinor-6-keto-prostaglandin F1 alpha (2,3D6KPGF1 alpha) using a monoclonal antibody and a horseradish peroxidase-linked antigen.

DESIGN AND METHODS

Assay validation included optimization of the standard curve, antibody cross-reactivity, accuracy and imprecision studies together with preliminary measurement of clinical samples.

RESULTS

Optimal conditions of the standard curve (0.078-10.0 micrograms/L) used 2 mg/L of antibody and 3 micrograms/L of peroxidase conjugate in each well, at pH 7.2. The coefficient of variation of various concentrations of the standard curve averaged 6.8%. Antibody cross-reactivity was < 0.01% for related prostanoids. Recovery of known amounts (0.1-5.0 micrograms/L) of 2,3D6KPGF1 alpha added to an urinary sample was 101.2 +/- 6.3%. Imprecision studies with non-pregnant (0.24 microgram/L) and pregnant (2.5 micrograms/L) samples displayed an intraassay variability of 8.9 and 9.9%, and an interassay variability of 9.6 and 10.0%, respectively. Urinary measurements in the non-pregnant and pregnant states were similar to those previously reported. An apparent decreased concentration was observed early in pregnancy in future preeclampsia.

CONCLUSION

With similar precision and validity, our assay method is time- and cost-saving. Preliminary urinary measurements show that this analyte may be of interest as an early marker for preeclampsia.

Calcium supplementation prevents pregnancy-induced hypertension by increasing the production of vascular nitric oxide

Pregnancy-induced hypertension (PIH) remains a common cause of maternal and fetal morbidity and mortality. During the past 7 years, some progress has been made in the prevention of PIH. Specifically, clinical studies have shown that supplementation with calcium can significantly reduce the frequency of PIH, specially in populations with a low calcium intake. We have suggested that, in such a population, calcium supplementation is a safe and effective measure for reducing the frequency of PIH. Thus, the purpose of this article is to advance a hypothesis about the mechanism by which calcium supplementation reduces the risk of PIH. We propose that dietary calcium supplementation reduces the frequency of PIH by maintaining the serum ionized calcium level which is crucial for the production of endothelial nitric oxide, the increased generation of which maintains the vasodilatation that is characteristic of normal pregnancy.

Excretion of prostacyclin and thromboxane metabolites before, during, and after pregnancy-induced hypertension

The aim of the present study was to assess whether changes in prostacyclin (PGI2) and thromboxane (TXA2) generation precede the manifestation of pregnancy-induced hypertension (PH). The metabolites 6-oxo-PGF1 alpha and TXB2 were measured in the urine of 69 randomly selected pregnant women from 16-20 weeks of gestation (wg) until delivery and more than 6 weeks postpartum. Between 16-20 and 21-24 wg 6-oxo-PGF1 alpha excretion did not change in patients who later developed PIH (n = 6) but increased significantly in the control group (n = 63). In contrast, a marked rise in TXB2 excretion was found in the PIH group but not in controls. Thereafter significant differences between both groups persisted from 25 wg until delivery. The 6-oxo-PGF1 alpha/TXB2 ratio was below the 10th percentile from 21-24 wg until delivery in patients with developing PIH. The excretion of both metabolites was substantially lower in the non-pregnant state without any difference between patient groups. These results show an altered urinary excretion of both 6-oxo-PGF1 alpha and TXB2 preceding the onset of the disease. A pathophysiological role of PGI2 deficiency and increased TXA2 formation in PIH appears substantiated.

The role of reproductive hormones in vascular disease and hypertension

Review of pertinent research demonstrates a link between sex steroids and vascular disease. Evidence for this association includes: beneficial effect of estrogens on the blood lipids (elevation of high-density lipoproteins and lowering of low-density lipoproteins), adverse effect of high-dose synthetic estrogens on coagulation, vasodilating action of progesterone, and adverse effect of androgens and androgen-derived progestagens on lipoproteins. Natural steroids appear to differ in their impact from synthetic compounds; endogenous hormones from exogenous and parenterally administered preparations. Furthermore, steroids have different effects at different concentrations, doses, and ratios. Their actions also vary according to age, sex, pregnant or nonpregnant state, body weight, smoking, and other risk factors. In this article, the following areas will be considered in relation to the impact of sex steroids on cardiovascular phenomena and hypertension: menstrual cycle and its disturbances; amenorrhea and hyperandrogenism; pregnancy with its hyperdynamic state and a tendency to gestational hypertension; oral-contraception-induced, dose-related thromboembolic phenomena; menopause and estrogen deficiency states with increased incidence of atherogenesis; estrogen replacement therapy with its decrease in cardiovascular morbidity; other hormonal therapies which induce hypoestrogenism with its consequences. The evidence is emerging that hormonal modifications may be useful in the prevention of cardiovascular morbidity.

Plasma prostacyclin and thromboxane concentrations in 160 normotensive, hypotensive, and preeclamptic patients during pregnancy, delivery, and the post partum period

Plasma concentrations of 6-keto-prostaglandin F1 alpha, a stable metabolite of prostacyclin, and TxB2 were measured in 160 women during pregnancy (n = 106), delivery (n = 40), and in the postpartum period (n = 14). Fifty nine patients had normal blood pressure, 10 had mild and 9 severe preeclampsia while 38 patients were hypotensive. Normotensive patients were grouped according to their gestational age: 22-26 weeks (n = 22), 27-31 weeks (n = 22), and 32-38 weeks (n = 15). 20 patients were in early first stage of delivery (cervical dilatation < or = 5 cm), 20 patients in late first stage (cervical dilatation > or = 6 cm). The concentration (mean value +/- SEM) of the PGI2 metabolite tended to increase during pregnancy without reaching significance (218 +/- 11; 225 +/- 10; 250 +/- 15 pg/ml). At the same time, TxB2 showed a decrease, which was most pronounced at 27-31 weeks (65 +/- 15; 40 +/- 2; 48 +/- 4 pg/ml; p < 0.001). The ratio of PGI2/TxA2 increased in parallel (4.9 +/- 0.4; 6 +/- 0.4; 4 +/- 0.5). There was no difference in plasma concentrations of PGI2 (figure 4) and TxA2 in patients with normal blood pressure, mild preeclampsia and hypotension, whereas in severe preeclampsia, the plasma concentration of PGI2 was significantly lower (p < 0.001) and of TxA2 significantly higher (p < 0.001). The ratio of PGI2/TxA2 shifted significantly to vasoconstriction in patients with severe preeclampsia (p < 0.0001) and to vasodilatation in those with hypotension (p < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of prostaglandins in obstetrical disorders

All pregnancy-associated tissues are capable of producing prostaglandins including PGI2 and TXA2. In normal pregnancy there is a dominance of PGI2 over TXA2 which may contribute to the maternal circulatory adaptation to pregnancy. Furthermore, both fetoplacental PGI2 and TXA2 production are important regulators of the fetal blood supply. It has been clearly established that in pre-eclampsia PGI2 production decreases in the fetoplacental tissues and quite probably also in the maternal tissues. The effect of this change may be further exaggerated by the simultaneous stimulation in pre-eclampsia of TXA2 production. The reason for PGI2 deficiency is not known. Other vasoactive agents, such as endothelin, may act in concert with prostaglandins. Relative PGI2 deficiency is likely to exist also in IUGR and lupus anticoagulant syndrome of pregnancy. In the latter, lupus anticoagulant may directly inhibit the synthesis of PGI2. One study suggests PGI2 deficiency also in early pregnancies of women with a history of repeated abortions. Prostaglandin production increases during full-term labour, and similar but smaller changes also occur in preterm labour. A silent bacterial infection may trigger the onset of preterm labour through cytokine-stimulated increase of prostaglandin production. No data were found on prostaglandin production in post-term pregnancies. That oligo-polyhydramnios is possibly prostaglandin mediated is suggested by the control of polyhydramnios by indomethacin treatment. Smoking decreases the production of PGI2 and possibly increases that of TXA2, which may lead to decreased blood flow and IUGR. Which constituent of cigarette smoke exerts this effect is not known. Ethanol consumption causes aberrations in prostaglandin metabolism which cannot be directly connected with fetal alcohol effects.

Cyclosporin reduces renal prostanoid excretion in type 1 diabetic patients

Prostacyclin and thromboxane A2 are important regulators of kidney blood flow. To examine whether changes in their metabolism could be involved in the nephrotoxicity of cyclosporin, we determined urinary excretion of 6-keto PGF1a and dinor-6-keto PGF1a (prostacyclin metabolites) and dinor-TxB2 (thromboxane metabolite) in five newly diagnosed type 1 diabetic patients during and after stopping cyclosporin therapy. In the resting state, cyclosporin had no effect on prostanoid excretion. In response to exercise, urinary excretion of 6-keto PGF1a was reduced by 50% (P less than 0.02), dinor-6-keto PGF1a by 15% (P less than 0.05) and dinor-TxB2 by 45% (P less than 0.02), while albumin excretion increased 4.5-fold (P less than 0.05) during cyclosporin therapy. Simultaneously, there was a rise in serum creatinine concentration, and renal biopsy specimens obtained from three patients showed periglomerular and interstitial fibrosis and tubular atrophy. After the discontinuation of cyclosporin therapy, serum creatinine concentrations returned to normal, histological changes improved and there was an associated rise in urinary prostanoid excretion. These data suggest that a reduction in renal prostanoid synthesis by cyclosporin may diminish renal blood flow and function, and lead to histological changes in the kidney.

Urinary excretion of prostacyclin and thromboxane metabolites in threatened preterm labor: effect of indomethacin and nylidrin

OBJECTIVE

We studied the role of smooth muscle-relaxing prostacyclin and its endogenous antagonist, thromboxane A2, in preterm labor by assessing the urinary output of the breakdown products of prostacyclin (6-keto-prostaglandin F1 alpha and 2,3-dinor-6-keto-prostaglandin F1 alpha) and those of thromboxane A2 (thromboxane B2, 2,3-dinor-thromboxane B2).

STUDY DESIGN

Thirty-three women in preterm labor between 25 and 34 weeks of gestation were studied before, during, and after treatment with indomethacin (n = 16) or nylidrin (n = 17). Urinary prostanoid levels were determined by high-performance liquid chromatography followed by radioimmunoassay, and the excretion was expressed as nanograms of prostanoids per millimole of creatinine. Statistical analyses were done by paired and unpaired Student t test, by Spearman's correlation, and by Wilcoxon signed-rank test.

RESULTS

Preterm labor was accompanied by a median 32% higher output of prostacyclin and thromboxane A2 metabolites as compared with those in 25 controls. At 8 hours after the start of treatment indomethacin induced maximal drops in 6-keto-prostaglandin F1 alpha (70%), in dinor-6-keto-prostaglandin F1 alpha (60%), in thromboxane B2 (85%), and in dinor-thromboxane B2 (95%) excretion. Within 1 week after the cessation of indomethacin, output of prostacyclin metabolites had recovered to pretreatment values, whereas output of thromboxane A2 metabolites was yet lower than the pretreatment value. Nylidrin induced no change in the output of prostacyclin and thromboxane A2 metabolites.

CONCLUSION

Threatened preterm labor is associated with a rise in prostacyclin and thromboxane A2 synthesis. Indomethacin inhibits more thromboxane A2 than does prostacyclin synthesis. These findings may explain the fetal vascular changes during maternal indomethacin treatment.

Thromboxane dominance and prostacyclin deficiency in habitual abortion

To evaluate the significance of vasoactive prostanoids in habitual abortion, we measured urinary excretion of prostacyclin metabolites (6-keto-PGF1 alpha and 2,3-dinor-6-keto-PGF1 alpha) and of thromboxane A2 metabolites (TxB2 and 2,3-dinor-TxB2) during 25 pregnancies in 22 women with recurrent spontaneous abortion (RSA). The control group were 16 pregnant women with no history of abortion. Ultrasound examination at first follow-up appointment showed a living fetus in 23 pregnancies of women with RSA. 9 of these pregnancies ended in abortion; 14 continued to term as did all the pregnancies in the control group. Compared with controls, women with RSA had a lower (p less than 0.05) ratio of prostacyclin to thromboxane between weeks 4 and 7 of gestation and a lower (p less than 0.01) output of 2,3-dinor-6-keto-PGF1 alpha between weeks 8 and 11. Women whose pregnancies ended in abortion had higher (p less than 0.05) output of 2,3-dinor-TxB2 between weeks 4 and 7 of gestation and lower (p less than 0.01) excretion of 2,3-dinor-6-keto-PGF1 alpha between weeks 8 and 11 compared with women whose pregnancies proceeded to term. We conclude that deficiency of vasodilatory prostacyclin may be a factor in habitual abortion.

The effect of magnesium sulfate infusion on systemic and renal prostacyclin production

Recent in vitro studies have suggested that magnesium sulfate (MgSO4) infusions may increase prostacyclin production. We studied the effect of MgSO4 infusion on prostacyclin (PGI2) metabolite excretion in women with either pregnancy induced hypertension or preterm labor. Excretion of renal and systemic metabolites of PGI2 was measured prior to and following the start of MgSO4 infusion in the two groups. An increased in renal PGI2 metabolite preterm labor excretion was noted in the hypertension group but no change was noted in systemic PGI2 excretion in either group. These data fail to support a generalized, short term increase in endothelial cell PGI2 production as the basis for the beneficial effect of MgSO4.

Prostacyclin versus thromboxane metabolite excretion: changes in pregnancy and labor

Urinary TXB2 and 6-keto-PGF1 alpha were measured by high pressure liquid chromatography combined with radioimmunoassay, in order to determine whether or not urinary excretion of 6-keto-PGF1 alpha and TXB2 followed a same pattern in pregnancy and labor. The excretion of 6-keto-PGF1 alpha was higher than that of TXB2 in both non-pregnant and pregnant women, but the ratio between them increased in pregnancy. The urinary excretion of both 6-keto-PGF1 alpha and TXB2 excretion was significantly increased (p less than 0.001) in pregnancy. Labor was associated with a much wider inter-individual variation in the excretion of 6-keto-PGF1 alpha and TXB2 than observed in pregnancy and in non-pregnant women. Also, the ratio between the two compounds varied more in labor than in pregnancy. The data indicate that the urinary levels of these two compounds do not follow a single well-determined pattern in pregnancy and labor.

Urinary excretion of prostacyclin and thromboxane degradation products in patients with ovarian malignancy: effect of cytostatic treatment

We studied the effect of ovarian cancer and its chemotherapy on the urinary excretion of prostacyclin (PGI2) and thromboxane A2 (TxA2) hydration and metabolic products. In six patients we measured 6-keto-PGF1 alpha and 2,3-dinor-6-keto-PGF1 alpha (PGI2 products) and thromboxane B2 (TxB2) and 2,3-dinor-TxB2 (TxA2 products) by HPLC followed by radioimmunoassay before, during and after the combined infusion of cisplatin, 4'epi-adriamycin and cyclophosphamide. Before the first cytostatic infusion, the urinary excretion of prostanoids was on average 4.4-5.8 times higher than in patients with ovarian endometriosis (n = 19). The infusion of cytostatics led to a 50-120% rise in the excretion of prostanoids during the first post-infusion 9 hours, but in the subsequent 10 hours their output was 25-45% below the initial value and remained low for at least 2 weeks. Following repetitive courses of cytostatics (2-4 per patient), prostanoid excretion tended to normalise. These data suggest that ovarian cancer is associated with increased production of PGI2 and TxA2, and that cytostatics suppress this production. This may be of biological significance in tumour behaviour and in the effect of cytostatics.

Preeclampsia: a hyperdynamic disease model

Preeclampsia is a common disease and as such is a significant contributor to maternal and neonatal morbidity and mortality. Despite the ubiquity of the disease and its public health impact, no comprehensive mechanism has been established. Therapy has been limited to bed rest and premature delivery. The purpose of this article is to examine preeclampsia from a hemodynamic point of view and to advance a hypothesis of disease mechanism.

Pregnancy-induced hypertension: current concepts

This brief review outlines current concepts concerning the aetiology and pathophysiology of pregnancy-induced hypertension and, based upon these concepts, presents a plan of intensive care management for the severe forms of this condition.

Changes in urinary 6-keto-prostaglandin F1 alpha excretion during pregnancy and labor

Urinary excretion of 6-keto-PGF1 alpha was measured by high pressure liquid chromatography and radioimmunoassay at various stages of pregnancy and labor. In the first trimester of pregnancy, urinary 6-keto-PGF1 alpha concentrations were not different from those measured before pregnancy, but they showed a significant increase in the second trimester of pregnancy (p less than 0.001). The levels rose further in the third trimester, although this increase was not statistically significant when compared to levels obtained in the second trimester. There was no evidence for a significant change in 6-keto-PGF1 alpha excretion with the onset of labor. During well-established, progressive labor mean values of 6-keto-PGF1 alpha excretion were about twice as high as before the onset of labor, but the range of values during labor was so wide that there was no statistical difference with values obtained in the second half of pregnancy. It is concluded that the increase in the urinary excretion of 6-keto-PGF1 alpha occurs later in pregnancy than the increase in TXB2 excretion and that labor at term is not associated with marked changes in 6-keto-PGF1 alpha excretion.

Urinary excretion of 6-keto prostaglandin F1 alpha in pre-eclampsia

In order to investigate whether urinary excretion of prostaglandins (PG) is involved in the pathophysiology of pre-eclampsia, urinary immunoreactive 6-keto PGF1 alpha and TXB2 were measured in normal and pre-eclamptic women by radio-immunoassay after extraction with Bond Elut column. Urinary levels of 6-keto PGF1 alpha and TXB2 were expressed as ratio of urinary concentration of prostaglandin vs. creatinine (pg prostaglandin/mg creatinine; pg/mg cre.). Urinary excretion in normal pregnant and postpartum women were 211.2 +/- 33.8 and 160.1 +/- 9.1 pg/mg cre., respectively. In the pre-eclamptic group, urinary excretion of 6-keto PGF1 alpha was 105.3 +/- 28.2 pg/mg cre. in pregnancy and 99.0 +/- 12.5 pg/mg cre. in the postpartum period. Urinary excretion of 6-keto PGF1 alpha in the pre-eclamptic group was significantly lower (P less than 0.05) than in normal controls during pregnancy but not in the postpartum period. Urinary excretion of TXB2 was not significantly different between the two groups. The urinary excretion of 6-keto PGF1 alpha was measured before and after the onset of pre-eclampsia in four cases of edema and weight gain of more than 500 g/week (group e), one case of proteinuria of more than 200 mg/dl with edema (group ep) and three cases of pre-eclampsia (group eph). The urinary excretion of 6-keto PGF1 alpha in these eight patients before onset of pre-eclampsia was slightly lower than of normal controls but not significantly so. In group eph, urinary excretion of PG was decreased after the onset of pre-eclampsia. These results provide further evidence of the involvement of PG in the pathophysiology of pre-eclampsia.

Increase in urinary thromboxane excretion during pregnancy and labor

Urinary TXB2 excretion was measured during pregnancy and labor using high pressure liquid chromatography and radioimmunoassay. From the first trimester onwards TXB2 levels in urine of pregnant women (n = 60) were significantly (p less than 0.001) higher than in non-pregnant women (n = 12) and they increased, albeit not significantly, with advancing gestation. Labor was associated with a two-fold increase in urinary TXB2 excretion. Levels in established labor were significantly higher than at any other time in pregnancy (p less than 0.001), but the levels in incipient labor showed considerable overlap with these in late pregnancy. Thus urinary TXB2, while not necessarily originating from the pregnant uterus, appears to reflect the uterine activity of labor and may be the expression of a general stimulation of prostanoid production during parturition.