[The cardiovascular paradox of pregnancy]

Mineralocorticoids participate in the reduced vascular reactivity of pregnant rats

The renin-angiotensin-aldosterone (RAA) system is markedly activated in pregnancy. We evaluated if mineralocorticoid receptors (MR), a major component of the RAA system, are involved in the reduced vascular reactivity associated with pregnancy. Canrenoate (MR antagonist; 20 mg·kg(-1)·day(-1)) was administered to nonpregnant (NP) rats for 7 days and to pregnant rats from day 15 to 22 of gestation. These were killed on day 17, 19, or 22 of gestation and, for NP rats, after 7 days treatment. Constrictor responses to phenylephrine (PhE) and KCl were measured in endothelium-denuded thoracic aortic rings under the influence of modulators of potassium (activators) and calcium (blocker) channels. Responses to the constrictors were blunted from days 17 to 22 of gestation. Although canrenoate increased responses to PhE and KCl, it did not reverse their blunted responses in gestation. NS-1619 and cromakalim (respectively, high-conductance calcium-activated potassium channels and ATP-sensitive potassium channel activators) diminished responses to both PhE and KCl. Inhibition by NS-1619 on responses to both agonists was decreased under canrenoate treatment in NP, but the reduced influence of NS-1619 during gestation was reversed by the mineralocorticoid antagonist. Cromakalim reduced the response to PhE significantly in the pregnant groups; this effect was enhanced by canrenoate. Finally, nifedipine (calcium channel blocker) markedly reduced KCl responses but to a lesser extent at the end of pregnancy, an inhibiting effect that was increased with canrenoate treatment. These data demonstrate that treating rats with a MR antagonist increased vascular reactivity but that it differentially affected potassium and calcium channel activity in aortas of NP and pregnant animals. This suggests that aldosterone is one of the components involved in vascular adaptations to pregnancy.

Longitudinal study of the renin angiotensin aldosterone system in purebred Spanish broodmares during pregnancy

During pregnancy, the coordinated interaction of the components of the renin-angiotensin-aldosterone system (RAAS) plays a vital role in accommodating the cardiovascular, haemodynamic and haematological needs imposed by foetal development and the placenta. This significantly influences the birth weight of the neonate and foetal viability. Although the evolution of each of the components of this system has been widely described in various species, it has not yet been clarified in the mare. Thus, the objectives of the present research were: 1) to establish reference values for renin (REN), angiotensin II (ANG-II) and aldosterone (ALD) concentrations in Spanish broodmares, and 2) to analyse the evolution of the aforementioned components during pregnancy. Thirty-one Purebred Spanish broodmares aged between 5 and 15 years old were studied for 11 months of pregnancy and compared to a control group composed of 11 non-pregnant Spanish mares. Morning venous blood samples were drawn on a monthly basis during pregnancy and pre-treated to prevent degradation until subsequent analysis. Serum REN, ANG-II and ALD concentrations were analysed by competitive immunoassay. This study found that pregnancy in Purebred Spanish broodmares is characterised by a gradual increase in REN concentrations, variable fluctuations in ALD concentrations, and no significant modifications in ANG-II concentrations. These results could provide potentially valuable information in understanding the physiological basis of the RAAS in mares, since we have been able to establish specific reference ranges for these components, as well as obtaining information on their evolution during pregnancy. As is often the case in other animal species, the increase in RAAS activity is a natural physiological process that occurs during pregnancy in Spanish broodmares. This may also be related to certain metabolic and hormone responses that contribute to the control of homeostasis in pregnant mares.

Effects of pregnancy, hypertension and nitric oxide inhibition on rat uterine artery myogenic reactivity

BACKGROUND/AIMS

The purpose of this study was to examine the effects of hypertension and nitric oxide (NO) inhibition on myogenic tone in uterine arteries during pregnancy.

METHODS

Premyometrial radial uterine arteries from nonpregnant and late pregnant Sprague-Dawley rats were evaluated for myogenic reactivity from the following groups: control, hypertensive/NO-inhibited (L-NAME treatment) and normotensive/NO-inhibited (L-NAME plus hydralazine).

RESULTS

In both nonpregnant and pregnant animals, L-NAME treatment significantly elevated blood pressures, while the addition of hydralazine made the animals normotensive. In nonpregnant animals, little myogenic tone was seen in controls; tone increased significantly in the L-NAME group, and was attenuated in those treated with L-NAME plus hydralazine. In pregnant animals, controls developed significant tone; this was reduced in the L-NAME group, and returned to control levels in the L-NAME plus hydralazine group.

CONCLUSIONS

Dimensional measurements showed that arteries from the pregnant hypertensive group did not undergo expansive remodeling, suggesting that tone development is related to phenotypic alterations in vascular smooth muscle and/or altered physical forces secondary to adaptive changes in arterial diameter. These differences implicate pregnancy-specific pathways in the development and inhibition of myogenic tone, and point to potentially opposing roles of NO and hypertension.

Gestation-induced uterine vascular remodeling

Uterine blood supply is a critical issue for fetal well-being, since it carries all the nutrients, including O2, required for fetal growth and gets rid of several fetal waste products. During pregnancy, uterine blood flow increases by almost 20 times and this is permitted by marked remodeling of the vessel wall. In the rat, uterine arterial remodeling takes place in the last 7-8 days of gestation (over 22) and is reversible in the postpartum period upon a similar time frame. It was also described as both hypertrophy and hyperplasia of all the constituents of the vascular wall. Several hypotheses have been proposed to explain such a phenomenon, including the driving role not only of sexual steroid hormones, progesterone and estrogens, but also of trophic factors of fetal origin. We have shown that alterations of the renin-angiotensin-aldosterone system, by manipulating sodium intake in the rats, reduced the pregnancy-induced remodeling of uterine arteries. These maneuvres resulted in the birth of pups that had characteristics of intrauterine growth restriction or in the development in the mother of "experimental" gestational hypertension, depending on, respectively, restriction or increased of sodium intake.

Female reproductive disorders: the roles of endocrine-disrupting compounds and developmental timing

OBJECTIVE

To evaluate the possible role of endocrine-disrupting compounds (EDCs) on female reproductive disorders emphasizing developmental plasticity and the complexity of endocrine-dependent ontogeny of reproductive organs. Declining conception rates and the high incidence of female reproductive disruptions warrant evaluation of the impact of EDCs on female reproductive health.

DESIGN

Publications related to the contribution of EDCs to disorders of the ovary (aneuploidy, polycystic ovary syndrome, and altered cyclicity), uterus (endometriosis, uterine fibroids, fetal growth restriction, and pregnancy loss), breast (breast cancer, reduced duration of lactation), and pubertal timing were identified, reviewed, and summarized at a workshop.

CONCLUSION(S)

The data reviewed illustrate that EDCs contribute to numerous human female reproductive disorders and emphasize the sensitivity of early life-stage exposures. Many research gaps are identified that limit full understanding of the contribution of EDCs to female reproductive problems. Moreover, there is an urgent need to reduce the incidence of these reproductive disorders, which can be addressed by correlative studies on early life exposure and adult reproductive dysfunction together with tools to assess the specific exposures and methods to block their effects. This review of the EDC literature as it relates to female health provides an important platform on which women's health can be improved.