The blood pressure response to infusions of angiotensin II during normal pregnancy: relation to plasma angiotensin II concentration, serum progesterone level, and mean platelet volume

Angiotensin-Converting Enzyme (ACE) Insertion/Deletion (I/D) Polymorphism as a Conjoint Regulator of Coagulation, Fibrinolytic, and RAAS Pathway in Infertility and Associated Pregnancy Complications

Despite the increase in assisted reproductive technologies, the high rates of infertility and pregnancy complications are a major concern to infertility specialists worldwide. Infertility may be attributed to pregnancy complications like thrombophilia, preeclampsia and fibrin-induced recurrent pregnancy loss (RPL). Renin-angiotensin-aldosterone system (RAAS) directly or indirectly causes preeclampsia and thrombophilia through the fibrinolytic pathway that ultimately leads to RPL or infertility. The underlying mechanisms of this interaction are still unclear. The present comprehensive review is intended to demonstrate the role and interaction of RAAS and fibrinolytic pathways in pregnancy complications. How this interaction can induce pregnancy complications, and ultimately infertility, is also discussed in the light of current evidence. This study also presents common markers that link RAAS and fibrinolytic processes in developing thrombophilia, preeclampsia and RPL. The common link in these pathways is ACE gene I/D polymorphism. Apart from ACE, PAI-1, VIIa, XIIa, AT1R, AT1AA, and TF are common molecules that can delineate the underlying causes of pregnancy complications and infertility.

The expression and activation of sex steroid receptors in the preeclamptic placenta

Estrogen and progesterone are the main pregnancy hormones produced by the placenta. It is well understood that estrogen stimulates angiogenesis in the uterus during the reproductive cycle. Although the estrogen and progesterone signaling pathways are assumed to be associated with placental vascularization and preeclampsia, expression of estrogen receptors (ESRs) and progesterone receptor (PGR) in the placenta have not been well studied. The present study examined the expression patterns of steroid hormone receptors in placentas. Human placenta samples were collected and divided into normal and preeclampsia groups. Results revealed that expression levels of ESR1 were reduced, whereas ESR2 and PGR were elevated in preeclamptic placentas. To generate an in vitro preeclampsia environment, human placenta‑derived BeWo cells were incubated under hypoxic conditions, or treated with catechol‑O‑methyl transferase inhibitor (COMT‑in) or L‑NG‑nitroarginine methyl ester (L‑NAME). Expression levels of ESR1, ESR2 and PGR in hypoxic cells demonstrated similar regulation as those in placentas from women with preeclampsia. Although COMT‑in and L‑NAME did not significantly regulate the expression levels of the receptors, COMT‑in translocated ESR2 and PGR from the nucleus to the cytoplasm, indicating that these receptors were inactivated. These results suggested that ESRs and PGR are associated with symptoms of preeclampsia in the placenta. The expression of ESR1 was reduced in preeclamptic placenta and hypoxic BeWo cells. In addition, the activation of ESR2 and PGR was blocked in placenta cells subjected to COMT‑in treatment. The reduced ESR1 expression and inactivation of ESR2 and PGR proteins may affect the physiological complications of preeclampsia in the placenta.

Relationships between endogenous sex hormone concentrations and vascular function in postmenopausal women

CONTEXT

Differences in postmenopausal endogenous sex hormone concentrations are associated with varying risks of a growing number of common diseases. The relationships between postmenopausal endogenous sex hormone concentrations and vascular function are not well understood.

OBJECTIVE

We examined in postmenopausal women the relationships between endogenous sex hormone concentrations and both blood pressure (BP) and renal vascular resistance (RVR), at baseline and in response to infused angiotensin II (AngII). SUBJECTS, INTERVENTIONS, AND MAIN OUTCOME MEASURES: A total of 34 hypertensive, postmenopausal women were studied in low-sodium and/or high-sodium balance. Serum estradiol, serum progesterone, BP, and RVR were measured at baseline. BP and RVR were remeasured after AngII infusion.

RESULTS

In low-sodium balance, the increases in systolic and diastolic BP in response to infused AngII were blunted with increased serum progesterone concentrations (P < 0.05). The increase in RVR in response to infused AngII was also blunted with increased serum progesterone concentrations (P < 0.005). The relationships between progesterone concentration and vascular response to AngII were independent of age, body mass index, and estradiol concentration. There were no significant correlations between estradiol concentration and BP or RVR response to AngII. There were no significant correlations between sex hormone concentrations and baseline BP or RVR. In high-sodium balance, there were no significant associations between sex hormone concentrations and vascular measures.

CONCLUSIONS

In postmenopausal women in low-sodium balance, the pressor and renovascular responses to AngII are blunted with increased endogenous progesterone concentrations. Our findings suggest a role for endogenous progesterone in modulating vascular function, even within the low postmenopausal range.

Progesterone for preventing pre-eclampsia and its complications

BACKGROUND

In the past, progesterone has been advocated for prevention of pre-eclampsia and its complications. Although progestogens are not used for this purpose in current clinical practice, it remains relevant to assess the evidence on their possible benefits and harms.

OBJECTIVES

To assess the effects of progesterone during pregnancy on the risk of developing pre-eclampsia and its complications.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (April 2006), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2006, Issue 2), and EMBASE (1974 to August 2005).

SELECTION CRITERIA

Randomised trials evaluating progesterone or any other progestogen during pregnancy for prevention of pre-eclampsia and its complications were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion and extracted data.

MAIN RESULTS

Two trials of uncertain quality were included (296 women). These trials compared progesterone injections with no progesterone. There was insufficient evidence to demonstrate any clear differences between the two groups on the risk of pre-eclampsia (one trial, 128 women; relative risk (RR) 0.21, 95% confidence interval (CI) 0.03 to 1.77), death of the baby (two trials, 296 women; RR 0.72, 95% CI 0.21 to 2.51), preterm birth (one trial, 168 women; RR 1.10, 95% CI 0.33 to 3.66), small-for-gestational-age babies (one trial, 168 women; RR 0.83, 95% CI 0.19 to 3.57) or major congenital defects (one trial, 168 women; RR 1.65, 95% CI 0.28 to 9.62). There were no reported cases of masculinisation of female babies (one trial, 128 women). Long-term follow up for the children has been reported in one trial, but the data are excluded from the review as 54% were lost to follow up at one year and 80% at 16 years.

AUTHORS' CONCLUSIONS

There is insufficient evidence for reliable conclusions about the effects of progesterone for preventing pre-eclampsia and its complications. Therefore, progesterone should not be used for this purpose in clinical practice at present. Unless new and plausible hypotheses emerge for the role of progesterone in development of pre-eclampsia, further trials of progesterone are unlikely to be a priority.

Systemic hypertension among women with uterine leiomyomata: potential final common pathways of target end-organ remodeling

The uterus and the heart share a common structure and may remodel in a similar fashion, albeit temporally distinct. The authors investigated the prevalence of systemic hypertension in women with uterine leiomyomata (fibroids) and compared the prevalence in women undergoing hysterectomy for other reasons as well as in age-matched women from the National Health and Nutrition Examination Survey III (NHANES III). A total of 584 women, 205 with leiomyomata in 1999 (group A) and 379 who underwent hysterectomy for a variety of reasons in 2000 (group B) at Advocate Christ Medical Center were included. Presence of leiomyomata was confirmed by pathology. Hypertension was defined as blood pressure > or = 140/90 mm Hg or history of hypertension with or without medication use. The prevalence of hypertension in group A and B patients with leiomyomata compared with NHANES III overall was 48.6% vs. 24% (p<0.001), in African Americans 55.5% vs. 32.4% (p<0.001), and in Caucasians 51.1% vs. 23.3% (p<0.001). Leiomyomata were more frequent among hypertensive than normotensive women (57% vs. 27%). Caucasian and African-American women with leiomyomata were significantly younger and more likely to use hormone replacement therapy than others. Thus there appears to be an association between leiomyomata and hypertension, which needs to be explored in future prospective trials.

Hypertensive Disorders of Pregnancy

Hypertensive disorders occur in 6% to 8% of all pregnancies, are the second leading cause of maternal death, and contribute to significant neonatal morbidity and mortality. This is a problem not only in inpatient settings, as ambulatory and home-care nurses are increasingly being called upon to monitor women who are at high risk and may have hypertensive disorders. To prevent hypertension-induced problems in pregnant women, nurses must have strong assessment, advocacy, and counseling skills. Nurses also must provide care based on the latest national standards as described in this article.

The dynamics of glomerular filtration in the puerperium

We evaluated the glomerular filtration rate (GFR) during the second postpartum week in 22 healthy women who had completed an uncomplicated pregnancy. We used physiological techniques to measure GFR, renal plasma flow, and oncotic pressure and computed a value for the two-kidney ultrafiltration coefficient (K(f)). We compared these findings with those in pregnant women previously studied on the first postpartum day as well as nongravid women of reproductive age. Healthy female transplant donors of reproductive age permitted the morphometric analysis of glomeruli and computation of the single-nephron K(f). The aforementioned physiological and morphometric measurements were utilized to estimate transcapillary hydraulic pressure (Delta P) from a mathematical model of glomerular ultrafiltration. We conclude that postpartum day 1 is associated with marked glomerular hyperfiltration (+41%). A theoretical analysis of GFR determinants suggests that depression of glomerular capillary oncotic pressure, the force opposing the formation of filtrate, is the predominant determinant of early elevation of postpartum GFR. A reversal of the gestational hypervolemia and hemodilution, still evident on postpartum day 1, eventuates by postpartum week 2. An elevation of oncotic pressure in the plasma that flows axially along the glomerular capillaries to supernormal levels ensues; however, GFR remains modestly elevated (+20%) above nongravid levels. An analysis of filtration dynamics at this time suggests that a significant increase in Delta P by up to 16%, an approximately 50% increase in K(f), or a combination of smaller increments in both must be invoked to account for the persistent hyperfiltration.

Maternal-fetal flow, negative events, and preeclampsia: role of ACE I/D polymorphism

The risk for an adverse pregnancy outcome is markedly higher in women with history of preeclampsia. This may stem from impaired placentation in early gestation and from high impedance to flow in uteroplacental circulation. The renin-angiotensin system is one of the mediators of the remodeling of spiral arteries throughout pregnancy. The D allele of the Insertion/Deletion (I/D) polymorphism in the ACE gene has been associated with higher ACE activity, accounting for 47% of the total phenotypic variance of serum enzyme levels. To investigate whether the ACE I/D polymorphism affects maternal uteroplacental and fetal umbilical circulation and the pregnancy outcome in women with a history of preeclampsia, 106 women underwent Doppler examination of uterine arteries resistance index and umbilical artery pulsatility index at the 16th, 20th, and 24th weeks of gestation and were genotyped for the I/D polymorphism. This study found a difference in genotype distribution (P=0.0002) and allele frequency (P<0.0001) between women with and those without preeclampsia recurrence and fetal growth restriction as well as an association (P=0.0007) between DD genotype and risk of recurrent preeclampsia or fetal growth restriction. At the 16th, 20th, and 24th weeks, uterine artery resistance indexes were significantly lower in II, higher in DD, and intermediate in ID genotype carriers, whereas the umbilical artery pulsatility index values were significantly higher in the DD group in comparison to ID and II genotypes. The current study shows that the ACE I/D polymorphism affects uteroplacental and umbilical flows and the recurrence of an adverse pregnancy outcome in women with history of preeclampsia.

Nasal continuous positive airway pressure reduces sleep-induced blood pressure increments in preeclampsia

Preeclampsia is the predominant cause of admissions to neonatal intensive care. The diurnal blood pressure pattern is flattened or reversed in preeclampsia. We hypothesized that snoring and partial upper airway obstruction contribute to nocturnal rises in blood pressure. We tested this hypothesis by controlling sleep- induced upper airway flow limitation and snoring with nasal positive pressure. Eleven women with preeclampsia underwent two consecutive polygraphic sleep studies with simultaneous beat-to-beat blood pressure monitoring. Average blood pressure for the night overall and in each sleep stage was calculated. Sleep architecture was similar on the two study nights. Sleep-induced partial upper airway flow limitation occurred in all patients in the initial study. Autosetting nasal continuous positive airway pressure (CPAP) applied at a mean maximal pressure of 6 +/- 1 cm H(2)O eliminated flow limitation throughout sleep on the treatment night. Blood pressure was markedly reduced on the treatment night [(128 +/- 3)/(73 +/- 3)] when compared with the initial nontreatment study night [(146 +/- 6)/(92 +/- 4)], p = (0.007)/(0.002). We conclude that partial upper airway obstruction during sleep in women with preeclampsia is associated with increments in blood pressure, which can be eliminated with the use of nasal CPAP.

Vascular reactivity in preeclampsia

It has long been known that vascular reactivity is altered in preeclamptic patients compared with normal pregnant women. This change even occurs weeks earlier than any clinical manifestation of the disease. Many investigators believe that the conditions for the development of preeclampsia are set as early as the first trimester. These changes in vascular reactivity appear to be independent of the blood pressure because they also occur in chronic hypertensive women destined to have preeclampsia. This review focuses on these changes in vascular reactivity reported in preeclampsia. Increased reactivity of the blood vessels in preeclampsia has been described in most, but not all, studies. The cause for the differences in reactivity between vessels from preeclamptic and normal pregnant women is not known. However, it cannot be attributed solely and with certainty to abnormalities in endothelium-dependent relaxation or the nitric oxide system because the study results published to date remain contradictory. In addition to functional differences, vessels from normal pregnant and preeclamptic women show distinct mechanical properties.

Comparison of angiotensin II type 1 receptor blockade and angiotensin-converting enzyme inhibition in pregnant sheep during late gestation

1. The effects of antagonism of the maternal renin-angiotensin system (RAS) with either an angiotensin II type 1-(AT1) specific receptor blocker (GR138950) or an angiotensin-converting enzyme (ACE) inhibitor (captopril) were compared in chronically-catheterised ewes and their foetuses during late gestation. 2. Daily from 127 +/- 1 days of gestation until parturition at 145 +/- 2 days, each ewe received i.v. either GR138950 (3 mg kg-1; n = 10), captopril (3 mg kg-1; n = 6) or an equivalent volume of vehicle solution (0.9% w/v saline; n = 10). 3. Within 2 h of drug administration, GR138950 abolished the maternal, but not the foetal, pressor responses to angiotensin II (AII; 100-188 ng kg-1, i.v.; P < 0.05), whereas captopril abolished both the maternal and foetal pressor responses to angiotensin I (AI; 400-750 ng kg-1, i.v.; P < 0.05). 4. On the first day of treatment, maternal blood pressure decreased in all GR138950-treated (-21 +/- 4 mmHg; P < 0.05) and captopril-treated (-13 +/- 5 mmHg; P > 0.05) ewes at 2 h after drug administration. Captopril also significantly decreased foetal blood pressure by 5 +/- 1 mmHg (P < 0.05). However, foetal blood pressure in the GR138950-treated animals remained unchanged. Maternal and foetal heart rates were unaffected by any treatment. Uterine blood flow was significantly reduced within 2 h of both GR138950 (-130 +/- 20 ml min-1; P < 0.05) and captopril (-72 +/- 16 ml min-1; P < 0.05) administration. 5. On the first day of treatment, maternal arterial haemoglobin (Hb) concentration and oxygen (O2) content increased at 2 h in all GR138950-treated and captopril-treated ewes. Foetal arterial pH and oxygenation (O2 content, O2 saturation and Pao2) were reduced by a similar extent in both groups of drug-treated ewes. 6. After one week of daily GR138950 administration, maternal blood pressure decreased from a pretreatment value of 96 +/- 5 mmHg on day 1 to 79 +/- 2 mmHg by day 7 (P < 0.05). Captopril treatment had no long-term effect on maternal blood pressure. Although foetal blood pressure increased by 3 +/- 1 mmHg over a week of vehicle treatment (P < 0.05), no significant differences were observed between the long-term changes in foetal blood pressure in all three groups of animals. 7. There were no long-term effects of drug administration on maternal Hb concentration or oxygenation, or on the foetal haematological parameters. However, changes in maternal PaCo2 observed in the GR138950-treated (+1.4 +/- 0.5 mmHg; P < 0.05) and captopril-treated (+3.3 +/- 1.1 mmHg; P > 0.05) ewes were significantly different from those seen in the vehicle-treated animals (P < 0.05). 8. There were no apparent adverse effects of maternal GR138950 or captopril treatment on foetal viability. 9. The present study demonstrated that administration of either GR138950 or captopril to pregnant ewes effectively blocked the maternal RAS, and caused hypotension and a decrease in uterine blood flow. However, only captopril appeared to cross the placenta to influence directly the RAS of the sheep foetus. This suggests that the fall in foetal oxygenation observed after AT1-specific receptor blockade and ACE inhibition originates primarily from changes in the maternal and/or placental vasculature. Despite these changes, neither GR138950 nor captopril were detrimental to the outcome of pregnancy when foetal blood loss was kept to a minimum.

Brain angiotensin receptor subtypes in the control of physiological and behavioral responses

This review summarizes emerging evidence that supports the notion of a separate brain renin-angiotensin system (RAS) complete with the necessary precursors and enzymes for the formation and degradation of biologically active forms of angiotensins, and several binding subtypes that may mediate their diverse functions. Of these subtypes the most is known about the AT1 site which preferentially binds angiotensin II (AII) and angiotensin III (AIII). The AT1 site appears to mediate the classic angiotensin responses concerned with body water balance and the maintenance of blood pressure. Less is known about the AT2 site which also binds AII and AIII and may play a role in vascular growth. Recently, an AT3 site was discovered in cultured neoblastoma cells, and an AT4 site which preferentially binds AII(3-8), a fragment of AII now referred to as angiotensin IV (AIV). The AT4 site has been implicated in memory acquisition and retrieval, and the regulation of blood flow. In addition to the more well-studied functions of the brain RAS, we review additional less well investigated responses including regulation of cellular function, the modulation of sensory and motor systems, long term potentiation, and stress related mechanisms. Although the receptor subtypes responsible for mediating these physiologies and behaviors have not been definitively identified research efforts are ongoing. We also suggest potential contributions by the RAS to clinically relevant syndromes such as dysfunctions in the regulation of blood flow and ischemia, changes in cognitive affect and memory in clinical depressed and Alzheimer's patients, and angiotensin's contribution to alcohol consumption.

Lactation affects pressor, volumetric and natriuretic responses to angiotensin II in goats

Demands on cardiovascular function and fluid turnover increase during lactation and pregnancy in the goat, but the hormonal status is different. This study is aimed at investigating the effects of hypertensive angiotensin II (ANGII) in lactating goats. The results were compared with those of pregnancy and control conditions. ANGII (0.5 microgram min-1) was infused intravenously for 60 min (n = 6). The rise in blood pressure in response to ANGII was attenuated during lactation as in pregnancy (P < 0.001 vs control period). ANGII caused reflex bradycardia. Plasma protein concentration decreased by 7.5% during infusions in lactating goats (pregnancy: 9%; control period: 4.5%). Renal Na excretion increased by 260% (lactation), by 400% (pregnancy; n.s. vs. lactation), and by 800% (control period; P < 0.01 vs. lactation). The glomerular filtration rate was unchanged during ANGII infusions in lactating animals, but increased in the other periods. Effective renal plasma flow decreased. ANGII raised aldosterone from < 34.5 pmol l-1 to 539 +/- 80 pmol l-1 (lactation) and to 428 +/- 41 pmol l-1 (control; P < 0.05 vs. lactation), and from 72 +/- 9 to 651 +/- 103 pmol l-1 (pregnancy; P < 0.01 vs. lactation). Plasma progesterone was undetectable during lactation, but varied from 0 to 17 nmol l-1 during control conditions and was 16 +/- 1 nmol l-1 during pregnancy. Oestradiol 17 beta was 181 +/- 22 pmol l-1 in pregnant goats, and undetectable in lactating animals. In conclusion, lactation affects ANGII-induced changes in cardiovascular and fluid regulation, but in this period the effects were not related to progesterone or oestradiol 17 beta.