Control of vascular responsiveness during human pregnancy

Pathophysiology of Preeclampsia-Induced Vascular Dysfunction and Implications for Subclinical Myocardial Damage and Heart Failure

Tragically, preeclampsia is a leading cause of pregnancy-related complications and is linked to a heightened risk for morbid and fatal cardiovascular disease (CVD) outcomes. Although the mechanism connecting preeclampsia to CVD risk has yet to be fully elucidated, evidence suggests distinct pathways of early and late preeclampsia with shared CV risk factors but with profound differences in perinatal and postpartum risk to the mother and infant. In early preeclampsia, <34 weeks of gestation, systemic vascular dysfunction contributes to near-term subclinical myocardial damage. Hypertrophy and diastolic abnormalities persist postpartum and contribute to early onset heart failure (HF). This HF risk remains elevated decades later and contributes to premature death. Black women are at the highest risk of preeclampsia and HF. These findings support closer monitoring of women postpartum, especially for those with early and severe preeclampsia to control chronic hypertension and reduce the potentially preventable sequelae of heightened CVD and HF risk.

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.

Maternal plasma angiotensin 1-7 concentration is related to twin pregnancy chorionicity in the third trimester of pregnancy

Introduction

Twin gestation is related to a higher risk of hypertensive disorders in pregnancy with possible risk stratification depending on chorionicity. It may be related to differences in plasma renin-angiotensin-aldosterone components between monochorionic and dichorionic twin pregnancies. The study aimed to analyze the plasma ANG II and ANG 1-7 concentrations in women with monochorionic and dichorionic twin gestation.

Methods

A prospective observational study included 79 women between 32 and 34 weeks of gestation with twin pregnancy (31 with monochorionic gestation and 48 with dichorionic gestation). Angiotensin II and angiotensin 1-7 concentrations were measured in the collected blood samples.

Results

No significant differences were observed in angiotensin II concentrations between the dichorionic and monochorionic group with significantly higher levels of angiotensin 1-7 being observed in the dichorionic group. Angiotensin 1-7 level was higher than angiotensin II in 20 women (64.5%) in the monochorionic group and in 42 women (87.5%, p=0.01) in the dichorionic group. Higher plasma concentrations of angiotensin II and lower concentrations of angiotensin 1-7 were found in 5 women with gestational hypertension and in 3 with preeclampsia compared to normotensive women.

Discussion

It is the first study investigating angiotensin II and angiotensin 1-7 in twin pregnancies regarding chorionicity. Our results showed that plasma angiotensin 1-7 concentration was related to chorionicity, while plasma angiotensin II level was not. In most women with twin gestation angiotensin 1-7 concentration exceeded the concentration of angiotensin II. A switch in the relation between angiotensin II and angiotensin 1-7 was observed in hypertensive pregnant women.

Interaction of the pre- and postnatal environment in the maternal immune activation model

Adverse influences during pregnancy are associated with a range of unfavorable outcomes for the developing offspring. Maternal psychosocial stress, exposure to infections and nutritional imbalances are known risk factors for neurodevelopmental derangements and according psychiatric and neurological manifestations later in offspring life. In this context, the maternal immune activation (MIA) model has been extensively used in preclinical research to study how stimulation of the maternal immune system during gestation derails the tightly coordinated sequence of fetal neurodevelopment. The ensuing consequence of MIA for offspring brain structure and function are majorly manifested in behavioral and cognitive abnormalities, phenotypically presenting during the periods of adolescence and adulthood. These observations have been interpreted within the framework of the "double-hit-hypothesis" suggesting that an elevated risk for neurodevelopmental disorders results from an individual being subjected to two adverse environmental influences at distinct periods of life, jointly leading to the emergence of pathology. The early postnatal period, during which the caregiving parent is the major determinant of the newborn´s environment, constitutes a window of vulnerability to external stimuli. Considering that MIA not only affects the developing fetus, but also impinges on the mother´s brain, which is in a state of heightened malleability during pregnancy, the impact of MIA on maternal brain function and behavior postpartum may importantly contribute to the detrimental consequences for her progeny. Here we review current information on the interaction between the prenatal and postnatal maternal environments in the modulation of offspring development and their relevance for the pathophysiology of the MIA model.

Mouse models of preeclampsia with preexisting comorbidities

Preeclampsia is a pregnancy-specific condition and a leading cause of maternal and fetal morbidity and mortality. It is thought to occur due to abnormal placental development or dysfunction, because the only known cure is delivery of the placenta. Several clinical risk factors are associated with an increased incidence of preeclampsia including chronic hypertension, diabetes, autoimmune conditions, kidney disease, and obesity. How these comorbidities intersect with preeclamptic etiology, however, is not well understood. This may be due to the limited number of animal models as well as the paucity of studies investigating the impact of these comorbidities. This review examines the current mouse models of chronic hypertension, pregestational diabetes, and obesity that subsequently develop preeclampsia-like symptoms and discusses how closely these models recapitulate the human condition. Finally, we propose an avenue to expand the development of mouse models of preeclampsia superimposed on chronic comorbidities to provide a strong foundation needed for preclinical testing.

Hypertension in Pregnancy: What We Now Know

PURPOSE OF REVIEW

Hypertensive disorders of pregnancy remain a highly morbid condition that affects both the mother and fetus, complicate approximately 10% of pregnancies worldwide, and contribute to immediate and long-term cardiovascular outcomes. There is still much to learn regarding pathogenesis and treatment goals.

RECENT FINDINGS

There is updated information on the pathogenesis of preeclampsia and treatment thresholds for HTN in pregnancy. l-Kynurenine, a metabolite of the essential amino acid l-tryptophan, has been implicated in preeclampsia as decreased levels were found in a uninephrectomized pregnant mouse model of preeclampsia, where replacement of l-kynurenine rescued the preeclamptic state. Further, data from CHIPS (The Control of HTN in Pregnancy Study) and CHAP (Chronic HTN and Pregnancy) trials demonstrate not only the safety of lowering blood pressure to either a diastolic goal of 85 mmHg (CHIPS) or less than 160/105 mmHg (CHAP) without detriment to the fetus but the CHAPS trial has also shown a decrease in the rate of preeclampsia in the treatment group.

SUMMARY

We will summarize the different types of hypertensive disorders in pregnancy, updates on the pathogenesis of preeclampsia, and appropriate HTN management based on the latest evidence in order to better care for mother and child.

Primary aldosteronism in pregnancy

Primary aldosteronism (PA) is the most common form of secondary hypertension. Although hypertensive disorders seem to affect around 5-10% of pregnancies worldwide, literature counts less than 80 cases of PA diagnosed during the peri-partum period. In this review we discuss about current knowledge on pathophysiology, natural history, diagnosis and treatment of PA in pregnancy. Because of the physiologic changes in the renin-angiotensin-aldosterone system (RAAS) and the contraindication to both confirmatory test and subtype differentiation, diagnosis of PA during pregnancy is challenging and relies mostly on detection of low/suppressed renin and high aldosterone levels. The course of pregnancy in patients with PA is highly variable, ranging from progesterone-induced amelioration of blood pressure (BP) control to severe and resistant hypertension with potential maternal and fetal complications. Mineralcorticoid receptor antagonists (MRA) are the recommended and most effective drugs for treatment of PA. As the anti-androgenic effect of spironolactone can potentially interfere with sexual development, their prescription is not recommended during pregnancy. On the other side, eplerenone, has proven to be safe and effective in 6 pregnant women and may be added to conventional first line drug regimen in presence of resistant hypertension or persistent hypokalemia. Ideally, patients with unilateral forms of PA should undergo adrenalectomy prior to conception, however, when PA is diagnosed during pregnancy and medical therapy fails to adequately control hypertension or its complications, adrenalectomy can be considered during the second trimester in case of unilateral adrenal mass at MRI-scan.

The role of angiotensin II and relaxin in vascular adaptation to pregnancy

In brief

There is a pregnancy-induced vasodilation of blood vessels, which is known to have a protective effect on cardiovascular function and can be maintained postpartum. This review outlines the cardiovascular changes that occur in a healthy human and rodent pregnancy, as well as different pathways that are activated by angiotensin II and relaxin that result in blood vessel dilation.

Abstract

During pregnancy, systemic and uteroplacental blood flow increase to ensure an adequate blood supply that carries oxygen and nutrients from the mother to the fetus. This results in changes to the function of the maternal cardiovascular system. There is also a pregnancy-induced vasodilation of blood vessels, which is known to have a protective effect on cardiovascular health/function. Additionally, there is evidence that the effects of maternal vascular vasodilation are maintained post-partum, which may reduce the risk of developing high blood pressure in the next pregnancy and reduce cardiovascular risk later in life. At both non-pregnant and pregnant stages, vascular endothelial cells produce a number of vasodilators and vasoconstrictors, which transduce signals to the contractile vascular smooth muscle cells to control the dilation and constriction of blood vessels. These vascular cells are also targets of other vasoactive factors, including angiotensin II (Ang II) and relaxin. The binding of Ang II to its receptors activates different pathways to regulate the blood vessel vasoconstriction/vasodilation, and relaxin can interact with some of these pathways to induce vasodilation. Based on the available literature, this review outlines the cardiovascular changes that occur in a healthy human pregnancy, supplemented by studies in rodents. A specific focus is placed on vasodilation of blood vessels during pregnancy; the role of endothelial cells and endothelium-derived vasodilators will also be discussed. Additionally, different pathways that are activated by Ang II and relaxin that result in blood vessel dilation will also be reviewed.

Glomerular hyperfiltration

Circulating blood is filtered across the glomerular barrier to form an ultrafiltrate of plasma in the Bowman's space. The volume of glomerular filtration adjusted by time is defined as the glomerular filtration rate (GFR), and the total GFR is the sum of all single-nephron GFRs. Thus, when the single-nephron GFR is increased in the context of a normal number of functioning nephrons, single glomerular hyperfiltration results in 'absolute' hyperfiltration in the kidney. 'Absolute' hyperfiltration can occur in healthy people after high protein intake, during pregnancy and in patients with diabetes, obesity or autosomal-dominant polycystic kidney disease. When the number of functioning nephrons is reduced, single-nephron glomerular hyperfiltration can result in a GFR that is within or below the normal range. This 'relative' hyperfiltration can occur in patients with a congenitally reduced nephron number or with an acquired reduction in nephron mass consequent to surgery or kidney disease. Improved understanding of the mechanisms that underlie 'absolute' and 'relative' glomerular hyperfiltration in different clinical settings, and of whether and how the single-nephron haemodynamic and related biomechanical forces that underlie glomerular hyperfiltration promote glomerular injury, will pave the way toward the development of novel therapeutic interventions that attenuate glomerular hyperfiltration and potentially prevent or limit consequent progressive kidney injury and loss of function.

Severe Acute Respiratory Syndrome Coronavirus 2 Infection in Pregnancy. A Non-systematic Review of Clinical Presentation, Potential Effects of Physiological Adaptations in Pregnancy, and Placental Vascular Alterations

In December 2019, the novel Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) rapidly spread to become a pandemic. To date, increasing evidence has described the potential negative impact of SARS-CoV-2 infection on pregnant women. Although the pathophysiology of coronavirus disease 2019 (COVID-19) is not entirely understood, there is emerging evidence that it causes a severe systemic inflammatory response associated with vascular alterations that could be of special interest considering some physiological changes in pregnancy. Additionally, these alterations may affect the physiology of the placenta and are associated with pregnancy complications and abnormal histologic findings. On the other hand, data about the vaccine against SARS-CoV-2 are limited, but the risks of administering COVID-19 vaccines during pregnancy appear to be minimal. This review summarizes the current literature on SARSCoV2 virus infection, the development of COVID-19 and its relationship with physiological changes, and angiotensin-converting enzyme 2 (ACE2) function during pregnancy. We have particularly emphasized evidence coming from Latin American countries.

SARS- CoV-2 infection and oxidative stress in early-onset preeclampsia

SARS-CoV-2 causes coronavirus disease 2019 (COVID-19) also in pregnant women. Infection in pregnancy leads to maternal and placental functional alterations. Pregnant women with vascular defects such as preeclampsia show high susceptibility to SARS-CoV-2 infection by undefined mechanisms. Pregnant women infected with SARS-CoV-2 show higher rates of preterm birth and caesarean delivery, and their placentas show signs of vasculopathy and inflammation. It is still unclear whether the foetus is affected by the maternal infection with this virus and whether maternal infection associates with postnatal affections. The SARS-CoV-2 infection causes oxidative stress and activation of the immune system leading to cytokine storm and next tissue damage as seen in the lung. The angiotensin-converting-enzyme 2 expression is determinant for these alterations in the lung. Since this enzyme is expressed in the human placenta, SARS-CoV-2 could infect the placenta tissue, although reported to be of low frequency compared with maternal lung tissue. Early-onset preeclampsia (eoPE) shows higher expression of ADAM17 (a disintegrin and metalloproteinase 17) causing an imbalanced renin-angiotensin system and endothelial dysfunction. A similar mechanism seems to potentially account for SARS-CoV-2 infection. This review highlights the potentially common characteristics of pregnant women with eoPE with those with COVID-19. A better understanding of the mechanisms of SARS-CoV-2 infection and its impact on the placenta function is determinant since eoPE/COVID-19 association may result in maternal metabolic alterations that might lead to a potential worsening of the foetal programming of diseases in the neonate, young, and adult.

[Features of retinal blood flow in pregnant women with carbohydrate metabolism disorders]

Studying the condition of retinal blood flow in pregnant women with disorders of carbohydrate metabolism contributes to early detection of diabetic retinopathy (DR), which is necessary for timely treatment and preservation of high visual functions.

PURPOSE

To study retinal blood flow in pregnant women with disorders of carbohydrate metabolism using optical coherence tomography angiography (OCTA) in order to determine the criteria for manifestation and progression of DR.

MATERIAL AND METHODS

The study examined 203 pregnant women in the third trimester: 24 - with type 1 and 2 diabetes (T1D and T2D), 143 - with gestational diabetes (GD), and 36 apparently healthy women with physiological pregnancy that comprised the control group. OCTA imaging was performed on RTVue XR Avanti ("Optovue", USA) system using HD Angio Retina 6.0 mm² scan protocol. The whole image vessel density (wiVD), foveal vessel density (FVD), and foveal avascular zone (FAZ) area in the superficial capillary plexus were studied.

RESULTS

FVD was significantly lower in pregnant women with diabetes than in pregnant women with GD and in the control group, prompting an assumption that retinal microvascular regulation changes because of chronic disturbances of carbohydrate metabolism in such patients and due to development of microangiopathy. Statistically significant increase in FAZ area and decrease in wiVD were revealed in patients with DR compared to data from the group of pregnant women with diabetes but without DR, in the absence of differences in FVD. In 2 patients with T1D and no ophthalmoscopic signs of DR, OCTA revealed areas of nonperfusion in the posterior pole of the eye.

CONCLUSION

OCTA can help identify areas of retinal nonperfusion in the posterior pole of the eye in pregnant women with diabetes and no ophthalmoscopic signs of DR, and determine objective indications for timely retinal laser coagulation.

Role of ACE2 in pregnancy and potential implications for COVID-19 susceptibility

In times of coronavirus disease 2019 (COVID-19), the impact of severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2 infection on pregnancy is still unclear. The presence of angiotensin-converting enzyme (ACE) 2 (ACE2), the main receptor for SARS-CoV-2, in human placentas indicates that this organ can be vulnerable for viral infection during pregnancy. However, for this to happen, additional molecular processes are critical to allow viral entry in cells, its replication and disease manifestation, particularly in the placenta and/or feto-maternal circulation. Beyond the risk of vertical transmission, COVID-19 is also proposed to deplete ACE2 protein and its biological actions in the placenta. It is postulated that such effects may impair essential processes during placentation and maternal hemodynamic adaptations in COVID-19 pregnancy, features also observed in several disorders of pregnancy. This review gathers information indicating risks and protective features related to ACE2 changes in COVID-19 pregnancies. First, we describe the mechanisms of SARS-CoV-2 infection having ACE2 as a main entry door and current evidence of viral infection in the placenta. Further, we discuss the central role of ACE2 in physiological systems such as the renin-angiotensin system (RAS) and the kallikrein-kinin system (KKS), both active during placentation and hemodynamic adaptations of pregnancy. Significant knowledge gaps are also identified and should be urgently filled to better understand the fate of ACE2 in COVID-19 pregnancies and the potential associated risks. Emerging knowledge will be able to improve the early stratification of high-risk pregnancies with COVID-19 exposure as well as to guide better management and follow-up of these mothers and their children.

Prorenin periconceptionally and in pregnancy: Does it have a physiological role?

Pregnancy demands major cardiovascular, renal and endocrine changes to provide an adequate blood supply for the growing fetus. The renin-angiotensin-aldosterone system plays a key role in this adaptation process. One of its components, prorenin, is released in significant amounts from the ovary and uteroplacental unit. This review describes the sources of prorenin in the periconception period and in pregnancy, including its modulation by in-vitro fertilization protocols, and discusses its potential effects, among others focusing on preeclampsia. It ends with discussing the long-term consequences, even in later life, of inappropriate renin-angiotensin-aldosterone system activity in pregnancy and offers directions for future research. Ultimately, a full understanding of the role of prorenin periconceptionally and during pregnancy will help to develop tools to diagnose and/or prevent reproductive complications.

Renal and cardiovascular repercussions in preeclampsia and their impact on fluid management: a literature review

Preeclampsia is a multifactorial condition associated with significant morbidity and mortality. Fluid therapy in these patients is challenging since volume expansion may precipitate pulmonary edema, and fluid restriction may worsen renal function. Furthermore, cardiac impairment may introduce an additional component to the hemodynamic management. This article reviews the repercussions of preeclampsia on renal and cardiovascular systems and the development of pulmonary edema, as well as to discuss fluid management, focusing on the mitigation of adverse outcomes and monitoring alternatives. The literature review was carried out using PubMed, Embase, and Google Scholar databases from May 2019 to March 2020. Papers addressing the subjects of interest were included regardless of the publication language. There is a current trend towards restricting the administration of fluids in women with non-complicated preeclampsia. However, patients with preeclampsia may experience hemorrhagic shock, requiring volume resuscitation. In this case, hemodynamic monitoring is recommended to guide fluid therapy while avoiding complications.

Activation of angiotensin type 2 receptor attenuates testosterone-induced hypertension and uterine vascular resistance in pregnant rats†

Preeclampsia is a pregnancy-related hypertensive disorder with unclear mechanisms. While hypersensitivity to angiotensin II via vasoconstrictive angiotensin type-1 receptor (AT1R) is observed in preeclampsia, the importance of vasodilatory angiotensin type-2 receptor (AT2R) in the control of vascular dysfunction is less clear. We assessed whether AT1R, AT2R, and endothelial nitric oxide synthase (eNOS) expression are altered in placental vessels of preeclamptic women and tested if ex vivo incubation with AT2R agonist Compound 21 (C21; 1 μM) could restore AT1R, AT2R, and eNOS balance. Further, using a rat model of gestational hypertension induced by elevated testosterone, we examined whether C21 (1 μg/kg/day, oral) could preserve AT1R and AT2R balance and improve blood pressure, uterine artery blood flow, and vascular function. Western blots revealed that AT1R protein level was higher while AT2R and eNOS protein were reduced in preeclamptic placental vessels, and AT2R agonist C21 decreased AT1R and increased AT2R and eNOS protein levels in preeclamptic vessels. In testosterone dams, blood pressure was higher, and uterine artery blood flow was reduced, and C21 treatment reversed these levels similar to those in controls dams. C21 attenuated the exaggerated Ang II contraction and improved endothelium-dependent vasorelaxation in uterine arteries of testosterone dams. These C21-mediated vascular effects were associated with decreased AT1R and increased AT2R and eNOS protein levels. C21 also increased serum nitrate/nitrite and bradykinin production in testosterone dams and attenuated the fetoplacental growth restriction. Thus, AT1R upregulation and AT2R downregulation are observed in preeclampsia and testosterone model, and increasing AT2R activity could help restore AT1R and AT2R balance and improve gestational vascular function.

Prorenin periconceptionally and in pregnancy: Does it have a physiological role?

Pregnancy demands major cardiovascular, renal and endocrine changes to provide an adequate blood supply for the growing fetus. The renin-angiotensin-aldosterone system plays a key role in this adaptation process. One of its components, prorenin, is released in significant amounts from the ovary and uteroplacental unit. This review describes the sources of prorenin in the periconception period and in pregnancy, including its modulation by in-vitro fertilization protocols, and discusses its potential effects, among others focusing on preeclampsia. It ends with discussing the long-term consequences, even in later life, of inappropriate renin-angiotensin-aldosterone system activity in pregnancy and offers directions for future research. Ultimately, a full understanding of the role of prorenin periconceptionally and during pregnancy will help to develop tools to diagnose and/or prevent reproductive complications.

Severe Acute Respiratory Syndrome Coronavirus 2, COVID-19, and the Renin-Angiotensin System: Pressing Needs and Best Research Practices

The coronavirus disease 2019 (COVID-19) pandemic is associated with significant morbidity and mortality throughout the world, predominantly due to lung and cardiovascular injury. The virus responsible for COVID-19-severe acute respiratory syndrome coronavirus 2-gains entry into host cells via ACE2 (angiotensin-converting enzyme 2). ACE2 is a primary enzyme within the key counter-regulatory pathway of the renin-angiotensin system (RAS), which acts to oppose the actions of Ang (angiotensin) II by generating Ang-(1-7) to reduce inflammation and fibrosis and mitigate end organ damage. As COVID-19 spans multiple organ systems linked to the cardiovascular system, it is imperative to understand clearly how severe acute respiratory syndrome coronavirus 2 may affect the multifaceted RAS. In addition, recognition of the role of ACE2 and the RAS in COVID-19 has renewed interest in its role in the pathophysiology of cardiovascular disease in general. We provide researchers with a framework of best practices in basic and clinical research to interrogate the RAS using appropriate methodology, especially those who are relatively new to the field. This is crucial, as there are many limitations inherent in investigating the RAS in experimental models and in humans. We discuss sound methodological approaches to quantifying enzyme content and activity (ACE, ACE2), peptides (Ang II, Ang-[1-7]), and receptors (types 1 and 2 Ang II receptors, Mas receptor). Our goal is to ensure appropriate research methodology for investigations of the RAS in patients with severe acute respiratory syndrome coronavirus 2 and COVID-19 to ensure optimal rigor and reproducibility and appropriate interpretation of results from these investigations.

Human Placental Vascular Reactivity in Health and Disease: Implications for the Treatment of Pre-eclampsia

Adequate development of the placenta is essential for optimal pregnancy outcome. Pre-eclampsia (PE) is increasingly recognized to be a consequence of placental dysfunction and can cause serious maternal and fetal complications during pregnancy. Furthermore, PE increases the risk of neonatal problems and has been shown to be a risk factor for cardiovascular disease of the mother later in life. Currently, there is no adequate treatment for PE, mainly because its multifactorial pathophysiology remains incompletely understood. It originates in early pregnancy with abnormal placentation and involves a cascade of dysregulated systems in the placental vasculature. To investigate therapeutic strategies it is essential to understand the regulation of vascular reactivity and remodeling of blood vessels in the placenta. Techniques using human tissue such as the ex vivo placental perfusion model provide insight in the vasoactive profile of the placenta, and are essential to study the effects of drugs on the fetal vasculature. This approach highlights the different pathways that are involved in the vascular regulation of the human placenta, changes that occur during PE and the importance of focusing on restoring these dysfunctional systems when studying treatment strategies for PE.

Lower circulating angiotensin II levels are related to the severity of preeclampsia and its risk as disclosed by a specific bioassay

Preeclampsia is characterized by an increased sensitivity to angiotensin II (Ang II). We herein assessed whether serum Ang II levels measured by a new developed bioassay are associated with preeclampsia, its severity, and the risk for developing this disease.Using a cross-sectional design, we studied 90 pregnant women (30 healthy pregnant and 60 with preeclampsia [30 with- and 30 without severe features]). We also used a nested case-control study with 30 women who eventually developed preeclampsia and 31 normotensive controls. Serum samples were collected at diagnosis of preeclampsia or at 4-week intervals (from weeks 12th to 36th). Ang II was measured using a bioassay.At diagnosis of preeclampsia, serum Ang II concentrations were significantly lower in preeclampsia without and with severe features (P = .001 and P < .001, respectively) than in healthy pregnancy. In addition, Ang II was different in preeclampsia with severe features than in those without severe features (P = .048). Women who subsequently developed preeclampsia had lower Ang II levels than women with normal pregnancies, and these changes became significant at 24 weeks onward. The risk to developing preeclampsia was higher among women with Ang II concentration values in the lowest quartile of the control distribution from 12 weeks onward (odds ratio ranging from 3.8 [95% CI 1.3-11.1] to 6.5 [95% CI 1.6-26.9]).We concluded that concentrations of Ang II are markedly diminished at diagnosis of preeclampsia and are closely associated with the severity of disease. Changes in circulating levels of Ang II precede the clinical presentation of preeclampsia.

Physiological changes in pregnancy

Physiological changes occur in pregnancy to nurture the developing foetus and prepare the mother for labour and delivery. Some of these changes influence normal biochemical values while others may mimic symptoms of medical disease. It is important to differentiate between normal physiological changes and disease pathology. This review highlights the important changes that take place during normal pregnancy.

A novel marker in pregnant with preeclampsia: renalase

BACKGROUND

Preeclampsia is characterized by an increase in high blood pressure and decrease in GFR and proteinuria, however, the underlying mechanisms are still unclear. Renalase is a recently discovered protein implicated in regulation of blood pressure in humans.

MATERIALS AND METHODS

Plasma concentrations of serum renalase were measured in healthy controls, healthy pregnant and pregnant with preeclampsia matched for age, gestational age, in the third trimester of pregnancy. Serum renalase levels were compared in pregnant with and without preeclampsia and non-pregnant controls. Factors associated with serum renalase levels in pregnancies were also evaluated.

RESULTS

In healthy pregnant serum renalase levels were significantly higher than in controls. However, pregnant with preeclampsia had lower renalase levels than healthy controls. Serum renalase levels were inversely associated with blood pressure levels and positively correlated with glomerular filtration rate.

CONCLUSION

The results indicated that the development of preeclampsia in pregnant is accompanied by altered serum renalase levels. High blood pressure and kidney damage that characterize this disorder are mediated at least in part by low renalase levels.

Echocardiographic Assessment of Structural and Hemodynamic Changes in Hypertension-Related Pregnancy

BACKGROUND

Pregnancy induces dramatic cardiovascular changes in order to meet the increasing metabolic needs. Adaptive change of left ventricle (LV) might be modified in pregnancy complicated by hypertension.

METHODS

Data from 193 consecutive pregnant women were analyzed. Clinical and echocardiographic data were compared in normotensive and hypertensive women.

RESULTS

Significantly higher LV mass indexed by height was observed in hypertensive women compared with normotensive women (84 ± 21 g/m vs. 97 ± 20 g/m, p = 0.001). Diastolic function measured by the ratio of peak velocity of early diastolic transmitral blood flow to early diastolic mitral annular velocity was impaired in hypertensive women (11.0 ± 3.0 vs. 9.2 ± 2.5, p < 0.001). Such change was more prominent in women with gestational hypertension (GH) than those with chronic hypertension (CH). Heavy maternal weight was an independent factor associated with LV hypertrophy (LVH) in both normotensive and hypertensive women. Overt eccentric LVH was more frequent than concentric remodeling/hypertrophy (24% vs. 8.4%) in GH, while the opposite result was observed in CH (14% vs. 23%).

CONCLUSION

Hypertensive pregnancy is associated with significant LVH and diastolic dysfunction. CH seems to induce different LV remodeling pattern from GH. Heavy maternal weight during pregnancy might intensify the unfavorable remodeling of LV, particularly in hypertensive pregnancy.

Statement on pregnancy in pulmonary hypertension from the Pulmonary Vascular Research Institute

Pregnancy outcomes in patients with pulmonary hypertension remain poor despite advanced therapies. Although consensus guidelines recommend against pregnancy in pulmonary hypertension, it may nonetheless occasionally occur. This guideline document sought to discuss the state of knowledge of pregnancy effects on pulmonary vascular disease and to define usual practice in avoidance of pregnancy and pregnancy management. This guideline is based on systematic review of peer-reviewed, published literature identified with MEDLINE. The strength of the literature was graded, and when it was inadequate to support high-level recommendations, consensus-based recommendations were formed according to prespecified criteria. There was no literature that met standards for high-level recommendations for pregnancy management in pulmonary hypertension. We drafted 38 consensus-based recommendations on pregnancy avoidance and management. Further, we identified the current state of knowledge on the effects of sex hormones during pregnancy on the pulmonary vasculature and right heart and suggested areas for future study. There is currently limited evidence-based knowledge about both the basic molecular effects of sex hormones and pregnancy on the pulmonary vasculature and the best practices in contraception and pregnancy management in pulmonary hypertension. We have drafted 38 consensus-based recommendations to guide clinicians in these challenging topics, but further research is needed in this area to define best practices and improve patient outcomes.

Novel Electrocardiographic Patterns for the Prediction of Hypertensive Disorders of Pregnancy--From Pathophysiology to Practical Implications

Hypertensive disorders of pregnancy are a major cause of poor outcome, including placental abruption, organ failure, cerebrovascular accident and disseminated intravascular coagulation. These disorders are associated with increased fetal risk of intrauterine growth restriction, intrauterine death and prematurity. Electrocardiography (ECG) recently emerged as a useful tool to evaluate cardiovascular complications during pregnancy. Specifically, left atrial abnormalities detected by standard ECG are associated with a fourfold increased risk of developing hypertensive disorders during pregnancy. The mechanisms linking left atrial abnormality on ECG with hypertensive disorders are still elusive. Several mechanisms, possibly reflected by abnormal left atrial activation on ECG, has been suggested. These include increased reactivity to angiotensin II and up-regulation of angiotensin type 1 receptors, with activation of autoantibodies targeting these receptors.

Linking the old and new -- do angiotensin II type 1 receptor antibodies provide the missing link in the pathophysiology of preeclampsia?

Preeclampsia remains a leading cause of maternal and neonatal morbidity and mortality. The pathophysiology of preeclampsia remains poorly understood with various pathological mechanisms being implicated including the renin angiotensin system (RAAS), angiogenic pathways and various components of the immune system. Recently a pathogenic autoimmune factor has been identified in the form of auto-agonistic angiotensin II type 1 receptor antibodies (AT1-AA). AT1-AA have been studied in vitro and in vivo in various human and animal models and these data have provided compelling evidence for their role in preeclampsia. This review summarises the current literature surrounding the role of AT1-AA in preeclampsia and draws links between this relatively novel antibody to well-established pathological mechanisms including the immune system, the RAAS, angiogenic pathways and placental ischaemia.

Gap junction regulation of vascular tone: implications of modulatory intercellular communication during gestation

In the vasculature, gap junctions (GJ) play a multifaceted role by serving as direct conduits for cell-cell intercellular communication via the facilitated diffusion of signaling molecules. GJs are essential for the control of gene expression and coordinated vascular development in addition to vascular function. The coupling of endothelial cells to each other, as well as with vascular smooth muscle cells via GJs, plays a relevant role in the control of vasomotor tone, tissue perfusion and arterial blood pressure. The regulation of cell-signaling is paramount to cardiovascular adaptations of pregnancy. Pregnancy requires highly developed cell-to-cell coupling, which is affected partly through the formation of intercellular GJs by Cx43, a gap junction protein, within adjacent cell membranes to help facilitate the increase of uterine blood flow (UBF) in order to ensure adequate perfusion for nutrient and oxygen delivery to the placenta and thus the fetus. One mode of communication that plays a critical role in regulating Cx43 is the release of endothelial-derived vasodilators such as prostacyclin (PGI2) and nitric oxide (NO) and their respective signaling mechanisms involving second messengers (cAMP and cGMP, respectively) that are likely to be important in maintaining UBF. Therefore, the assertion we present in this review is that GJs play an integral if not a central role in maintaining UBF by controlling rises in vasodilators (PGI2 and NO) via cyclic nucleotides. In this review, we discuss: (1) GJ structure and regulation; (2) second messenger regulation of GJ phosphorylation and formation; (3) pregnancy-induced changes in cell-signaling; and (4) the role of uterine arterial endothelial GJs during gestation. These topics integrate the current knowledge of this scientific field with interpretations and hypotheses regarding the vascular effects that are mediated by GJs and their relationship with vasodilatory vascular adaptations required for modulating the dramatic physiological rises in uteroplacental perfusion and blood flow observed during normal pregnancy.

Hormones and hemodynamics in pregnancy

CONTEXT

Normal pregnancy is associated with sodium and water retention, which results in plasma volume expansion prior to placental implantation. The explanation offered for these events is that pregnancy 'resets' both volume and osmoreceptors.

EVIDENCE ACQUISITION

The mechanisms for such an enigmatic 'resetting' in pregnancy have not previously been explained. However, recent human pregnancy studies have demonstrated that the earliest hemodynamic change in pregnancy is primary systemic arterial vasodilation. This arterial underfilling is associated with a secondary increase in cardiac output and activation of the neurohumoral axis, including stimulation of the renin-angiotensin-aldosterone, sympathetic, and non-osmotic vasopressin systems. Resistance to the pressor effects of angiotensin and sympathetic stimulation in pregnancy is compatible with an increase in endothelial nitric oxide synthase activity.

RESULTS

In contrast to the sodium and water retention which occur secondary to the primary arterial vasodilation in cirrhosis, glomerular filtration and renal blood flow are significantly increased in normal pregnancy. A possible explanation for this difference in arterial vasodilation states is that relaxin, an arterial vasodilator which increases during pregnancy, has a potent effect on both systemic and renal circulation. Endothelial damage in pregnancy is pivotal in the pathogenesis of preeclampsia in pregnancy.

CONCLUSIONS

Against a background of the primary arterial vasodilation hypothesis, it is obvious that reversal of the systemic vasodilatation in pregnancy, without subsequent activation of the renin-angiotensin-aldosterone system (78), will evoke a reversal of all the links in the chain of events in normal pregnancy adaptation, thus, it may cause preeclampsia. Namely, a decrease of renal vasodilation will decrease glomerular filtration rate.

Association between urinary angiotensinogen, hypertension and proteinuria in pregnant women with preeclampsia

INTRODUCTION

Preeclampsia is a life-threatening disorder of pregnancy. The pathogenic mechanisms of preeclampsia remain uncertain. The aim of this study is to investigate the relation between urinary angiotensinogen (UAGT) levels, an indicator of local renin-angiotensin system (RAS) activity in the kidney, and blood pressure and urinary protein excretion in preeclampsia.

MATERIALS AND METHODS

For this study, 90 women aged between 20-39 years were recruited. Spot urine samples were collected to measure urinary angiotensinogen/creatinine ratio (UAGT/UCre). Log(UAGT/UCre) was compared in pregnancies with and without preeclampsia and non-pregnant controls. Factors affecting log(UAGT/UCre) in pregnancies were also investigated.

RESULTS

In all pregnancies log(UAGT/UCre) levels were significantly higher than in non-pregnant controls (0.58±0.19 vs. 0.33±0.14, respectively, p=0.002). However, log(UAGT/UCre) levels in pregnancies with preeclampsia were slightly lower than in normal pregnancies (0.52±0.18 vs. 0.64±0.19, respectively, p=0.012). Log(UAGT/UCre) levels were correlated positively with blood pressure and proteinuria in pregnancies with preeclampsia. However, log(UAGT/UCre) levels were not correlated with age, height, body weight, gestational age, body mass index, and serum creatinine.

CONCLUSION

This study showed that elevated local RAS activity in kidney was correlated with high blood pressure and proteinuria in preeclampsia. Local RAS activation in the kidneys may be one of the contributing factors in the development of preeclampsia.

Matrix metalloproteinases as drug targets in preeclampsia

Preeclampsia is an important syndrome complicating pregnancy. While the pathogenesis of preeclampsia is not entirely known, poor placental perfusion leading to widespread maternal endothelial dysfunction is accepted as a major mechanism. It has been suggested that altered placental expression of matrix metalloproteinases (MMPs) may cause shallow cytotrophoblastic invasion and incomplete remodeling of the spiral arteries. MMPs are also thought to link placental ischemia to the cardiovascular alterations of preeclampsia. In fact, MMPs may promote vasoconstriction and surface receptors cleavage affecting the vasculature. Therefore, the overall goal of this review article is to provide an overview of the pathophisiology of preeclampsia, more specifically regarding the role of MMPs in the pathogenesis of preeclampsia and the potential of MMP inhibitors as therapeutic options.

Disproportionate pregnancy-induced myocardial hypertrophy in women with essential hypertension

BACKGROUND

Pregnancy and arterial hypertension (AH) have a prohypertrophic effect on the heart. It is suspected that the 2 conditions combined cause disproportionate myocardial hypertrophy. We sought to evaluate myocardial hypertrophy (LVH) and left ventricular function in normotensive and hypertensive women in the presence or absence of pregnancy.

METHODS

This prospective cross-sectional study included 193 women divided into 4 groups: hypertensive pregnant (HTP; n = 57), normotensive pregnant (NTP; n = 47), hypertensive nonpregnant (HTNP; n = 41), and normotensive nonpregnant (NTNP; n = 48). After clinical and echocardiographic evaluation, the variables were analyzed using 2-way analysis of variance with pregnancy and hypertension as factors. Left ventricular mass (LVM) was compared using nonparametric analysis of variance and Dunn's test. Predictors of LVH and diastolic dysfunction were analyzed using logistic regression (significance level, P < 0.05).

RESULTS

Myocardial hypertrophy was independently associated with hypertension (odds ratio (OR) = 11.1, 95% confidence interval (CI) = 3.2-38.5; P < 0.001) and pregnancy (OR = 6.1, 95% CI = 2.6-14.3; P < 0.001) in a model adjusted for age and body mass index. Nonpregnant women were at greater risk of LVH in the presence of AH (OR = 25.3, 95% CI = 3.15-203.5; P = 0.002). The risk was additionally increased in hypertensive women during pregnancy (OR = 4.3, 95% CI = 1.7-10.9; P = 0.002) in the model adjusted for stroke volume and antihypertensive medication. Although none of the NTNP women presented with diastolic dysfunction, it was observed in 2% of the NTP women, 29% of the HTNP women, and 42% of the HTP women (P < 0.05).

CONCLUSIONS

Hypertension and pregnancy have a synergistic effect on ventricular remodeling, which elevates a woman's risk of myocardial hypertrophy.

The role of the renin-angiotensin-aldosterone system in preeclampsia: genetic polymorphisms and microRNA

The compensatory alterations in the rennin-angiotensin-aldosterone system (RAAS) contribute to the salt-water balance and sufficient placental perfusion for the subsequent well-being of the mother and fetus during normal pregnancy and is characterized by an increase in almost all the components of RAAS. Preeclampsia, however, breaks homeostasis and leads to a disturbance of this delicate equilibrium in RAAS both for circulation and the uteroplacental unit. Despite being a major cause for maternal and neonatal morbidity and mortality, the pathogenesis of preeclampsia remains elusive, where RAAS has been long considered to be involved. Epidemiological studies have indicated that preeclampsia is a multifactorial disease with a strong familial predisposition regardless of variations in ethnic, socioeconomic, and geographic features. The heritable allelic variations, especially the genetic polymorphisms in RAAS, could be the foundation for the genetics of preeclampsia and hence are related to the development of preeclampsia. Furthermore, at a posttranscriptional level, miRNA can interact with the targeted site within the 3'-UTR of the RAAS gene and thereby might participate in the regulation of RAAS and the pathology of preeclampsia. In this review, we discuss the recent achievements of genetic polymorphisms, as well as the interactions between maternal and fetal genotypes, and miRNA posttranscriptional regulation associated with RAAS in preeclampsia. The results are controversial but utterly inspiring and attractive in terms of potential prognostic significance. Although many studies suggest positive associations with genetic mutations and increased risk for preeclampsia, more meticulously designed large-scale investigations are needed to avoid the interference from different variations.

Renin-angiotensin system in pre-eclampsia: everything old is new again

This review presents an update of the role of the renin-angiotensin system in normal pregnancy and pre-eclampsia. We have known for years that the circulatory renin-angiotensin system in pre-eclampsia is suppressed. We now know that the circulating renin-angiotensin system does not only have a vasoconstrictor arm, but also a vasodilator arm, which is upregulated in normal pregnancy; this balance is probably disturbed in pre-eclampsia. Recent studies show the importance of the local renin-angiotensin system in the uteroplacental unit for early placentation and regulation of placental blood flow. We discuss the possible role of autoantibodies against the AT1-receptor in pre-eclampsia and the suggestion that activation of the AT1-receptor in the placenta may lead to placental dysfunction and the clinical syndrome of pre-eclampsia.

Preeclampsia and hypertensive disease in pregnancy: their contributions to cardiovascular risk

More women than men die each year of cardiovascular disease, which remains the leading cause of death in the United States. Sex-specific factors, including pregnancy-related disorders, should be considered when assessing cardiovascular (CV) risk in women. Hypertensive disorders of pregnancy have been associated with CV risk later in life and may identify women in whom earlier primary prevention may reduce their risk. This article reviews the physiologic changes in blood pressure during pregnancy, current definitions of hypertensive diseases of pregnancy and preeclampsia, and postulated pathophysiologic mechanisms leading to preeclampsia that might contribute to later CV risk. Also summarized are studies providing evidence on the association between hypertensive diseases of pregnancy and future CV risk.

Renin angiotensin signaling in normal pregnancy and preeclampsia

Many reports indicate that there is an increase in almost all of the components of the renin-angiotensin system (RAS) during an uncomplicated pregnancy, but renin activity, angiotensin II, and aldosterone decrease in preeclampsia (PE) for reasons that are unclear. PE is a life-threatening disorder of late pregnancy characterized by hypertension, proteinuria, increased soluble fms-like tyrosine kinase-1, as well as renal and placental morphologic abnormalities. Although a leading cause of maternal and perinatal morbidity and mortality, the pathogenic mechanisms of PE remain largely undefined. Immunologic mechanisms and aberrations of the RAS have been long considered contributors to the disorder. Bridging these two concepts, numerous studies report the presence of the angiotensin II type I receptor agonistic autoantibody (AT(1)-AA) found circulating in preeclamptic women. This autoantibody induces many key features of the disorder through AT(1) receptor signaling, and has been implicated in the pathogenesis of PE. Here we review the functions of the RAS during normal pregnancy and PE, and highlight the role of AT(1)-AA in both animal models and in the human disorder.

Role of the AT2 receptor in modulating the angiotensin II contractile response of the uterine artery at mid-gestation

INTRODUCTION

During human pregnancy, circulating concentrations of components of the renin-angiotensin system increase, but pressor refractoriness to angiotensin II (Ang-II) is observed. Given the importance of the Ang-II pressor response in deciding susceptibility to preeclampsia and of the Ang-II system for controlling uterine vasoreactivity, we sought to address the effects of pregnancy on the reactivity of the isolated uterine artery (UA) in mice.

MATERIALS AND METHODS

Blood pressure was measured throughout pregnancy in awake C57BL/6J mice. UA segments were isolated from three groups of animals (non-pregnant, mid [day 12-13] and late [day 18-19] gestation) and studied by wire myography.

RESULTS

UA diameters, KCl-mediated responses, and acetylcholine-dependent vasorelaxation were greater at mid and late gestation than in non-pregnant animals. Ang-II responses were also greater during pregnancy, with an increased contraction in response to AT2 receptor blockade at mid-gestation. AT1 receptor blockade abolished the Ang-II response in all groups.

CONCLUSIONS

Study findings are consistent with the possibility that AT2 receptor-mediated vasodilatation plays a role in modulating Ang-II contractile responses in pregnancy.

Hypertension in pregnancy: a comprehensive update

Hypertensive disorders of pregnancies remain a central public health concern throughout the world, and are a major cause of maternal mortality in the developing world. Although treatment options have not significantly changed in recent years, insight on the pathogenesis of preeclampsia/eclampsia has been remarkable. With improved animal models of preeclampsia and large-scale human trials, we have embarked upon a new era where angiogenic biomarkers based on mechanism of disease can be designed to assist in early diagnosis and treatment. There is also a growing recognition of how elusive the diagnosis of eclampsia can be, especially in the postpartum period. Proper treatment of these patients depends heavily on the correct diagnosis, especially by the emergency physician. Finally, large epidemiologic studies have revealed that preeclampsia, once thought to be a self-limited entity, now appears to portend real damage to the cardiovascular and other organ systems in the long term. This review will present the latest update on our understanding of the various hypertensive disorders of pregnancies and their treatment options.

The 2010 Canadian Cardiovascular Society guidelines for the diagnosis and management of heart failure update: Heart failure in ethnic minority populations, heart failure and pregnancy, disease management, and quality improvement/assurance programs

Since 2006, the Canadian Cardiovascular Society heart failure (HF) guidelines have published annual focused updates for cardiovascular care providers. The 2010 Canadian Cardiovascular Society HF guidelines update focuses on an increasing issue in the western world - HF in ethnic minorities - and in an uncommon but important setting - the pregnant patient. Additionally, due to increasing attention recently given to the assessment of how care is delivered and measured, two critically important topics - disease management programs in HF and quality assurance - have been included. Both of these topics were written from a clinical perspective. It is hoped that the present update will become a useful tool for health care providers and planners in the ongoing evolution of care for HF patients in Canada.

Outcomes of pregnancy in patients with preexisting postural tachycardia syndrome

BACKGROUND

Postural orthostatic tachycardia syndrome (POTS) occurs more commonly in women than in men and often affects women of childbearing age. Many of these women wish to have children, yet there are little reported data on the outcomes of pregnancy in patients with POTS. To date there has been one report of two patients with POTS who successfully completed pregnancy. We report the outcomes of 22 women with preexisting POTS who became pregnant.

OBJECTIVE

To assess the outcome of pregnancy in patients with preexisting POTS.

METHODS AND RESULTS

Twenty-two patients, age 30 +/- 7 years, with POTS became pregnant. Migraine was the common comorbidity found in 40% of patients. Medications used were beta-blockers (18%), midiodrine (31%), selective serotonin reuptake inhibitors (31%), fludrocortisone (13%), combination (40%), and none (18%). During pregnancy, symptoms of POTS remained unchanged in three (13%), improved in 12 (55%), and worsened in seven (31%) patients. One patient who had recurrent episodes of syncope without aura was found to have complete heart block and received a cardiac pacemaker. All patients completed pregnancy successfully. There were no stillbirths. One patient developed hyperemesis. Eighteen patients had vaginal delivery and four patients delivered by cesarian section. No other complications of pregnancy were encountered. Congenital abnormalities were encountered in the form of one atrial septal defect, one ventricular septal defect, and one Down's syndrome. Postpartum symptoms of POTS remained stable in 15 (69%) patients and worsened in seven (31%) patients.

CONCLUSION

Based on our observation, patients with POTS can safely complete pregnancy if they desire to do so. POTS should not be considered a contraindication to pregnancy per se.

Resistance artery adaptation to pregnancy counteracts the vasoconstricting influence of plasma from normal pregnant women

Using a rat model, we investigated the effects of circulating factors in pregnancy on cerebrovascular and systemic vascular function by comparing myogenic reactivity, tone, and endothelial vasodilator production of the posterior cerebral artery (PCA) and mesenteric artery (MA) of nonpregnant (NP) animals perfused with nonpregnant and pregnant human plasma. Arteries from late pregnant (LP) animals were then perfused similarly to evaluate a potential adaptive effect of pregnancy on vessel function. A 3-hour exposure to pregnant plasma caused increased myogenic reactivity and tone in vessels from NP animals and produced a decreased endothelium-derived hyperpolarizing factor response in NP PCAs, findings that were not seen with MAs. The increased reactivity and tone noted in NP vessels was abolished when pregnant plasma was perfused through LP arteries, suggesting these vessels adapt during pregnancy to the vasoconstricting influence of pregnant plasma.