Uterine blood flow responses to ICI 182 780 in ovariectomized oestradiol-17beta-treated, intact follicular and pregnant sheep

Oestrogen dramatically increases uterine blood flow (UBF) in ovariectomized (Ovx) ewes. Both the follicular phase and pregnancy are normal physiological states with elevated levels of circulating oestrogen. ICI 182 780 is a pure steroidal oestrogen receptor (ER) antagonist that blocks oestrogenic actions in oestrogen-responsive tissue. We hypothesized that an ER-mediated mechanism is responsible for in vivo rises in UBF in physiological states of high oestrogen. The purpose of the study was to examine the effect of an ER antagonist on exogenous and endogenous oestradiol-17beta (E2beta)-mediated elevations in UBF. Sheep were surgically instrumented with bilateral uterine artery blood flow transducers, and uterine and femoral artery catheters. Ovx animals (n = 8) were infused with vehicle (35% ethanol) or ICI 182 780 (0.1-3.0 microg min(-1)) into one uterine artery for 10 min before and 50 min after E2beta was given (1 microg kg(-1) I.V. bolus) and UBF was recorded for an additional hour. Intact, cycling sheep were synchronized to the follicular phase using progesterone, prostaglandin F2alpha(PGF2alpha) and pregnant mare serum gonadotrophin (PMSG). When peri-ovulatory rises in UBF reached near peak levels, ICI 182 780 (1 or 2 microg (ml uterine blood flow)-1) was infused unilaterally (n = 4 sheep). Ewes in the last stages of pregnancy (late pregnant ewes) were also given ICI 182 780 (0.23-2.0 microg (ml uterine blood flow)-1; 60 min infusion) into one uterine artery (n = 8 sheep). In Ovx sheep, local infusion of ICI 182 780 did not alter systemic cardiovascular parameters, such as mean arterial blood pressure or heart rate; however, it maximally decreased ipsilateral, but not contralateral, UBF vasodilatory responses to exogenous E2beta by approximately 55-60% (P < 0.01). In two models of elevated endogenous E2beta, local ICI 182 780 infusion inhibited the elevated UBF seen in follicular phase and late pregnant ewes in a time-dependent manner by approximately 60% and 37%, respectively; ipsilateral >> contralateral effects (P < 0.01). In late pregnant sheep ICI 182 780 also mildly and acutely (for 5-30 min) elevated mean arterial pressure and heart rate (P < 0.05). We conclude that exogenous E2beta-induced increases in UBF in the Ovx animal and endogenous E2beta-mediated elevations of UBF during the follicular phase and late pregnancy are partially mediated by ER-dependent mechanisms.

Endothelial vasodilator production by ovine uterine and systemic arteries: ovarian steroid and pregnancy control of ERalpha and ERbeta levels

Pregnancy and the follicular phase are physiological states of elevated oestrogen levels and rises in uterine blood flow (UBF). The dramatic increase in utero-placental blood flow during gestation is required for normal fetal growth and development. Oestrogen exerts its vasodilatory effect by binding to its specific oestrogen receptors (ER) in target cells, resulting in increased expression and activity of endothelial nitric oxide synthase (eNOS) to relax vascular smooth muscle (VSM). However, the regulation of endothelial versus VSM ERalpha and ERbeta expression in uterine arteries (UAs) during the ovarian cycle, pregnancy and with exogenous hormone replacement therapy (HRT) are currently unknown. ER mRNA and protein localization was determined by in situ hybridization (ISH) using 35S-labelled riboprobes and immunohistochemistry (IHC), respectively. UA endothelial (UAendo), UA VSM, omental artery endothelium (OA endo), and OA VSM proteins were isolated and ERalpha and ERbeta protein expression was determined by Western analysis. We observed by ISH and IHC that ERalpha and ERbeta mRNA and protein were localized in both UAendo and UA VSM. Immunoblot data demonstrated ovarian hormone specific regulation of ERalpha and ERbeta protein in UAendo and UA VSM. Compared to luteal phase sheep, both ERalpha and ERbeta levels in UAendo were elevated in follicular phase sheep. Whereas ERbeta was elevated by pregnancy in UAendo and UA VSM, ERalpha was not appreciably altered. eNOS was increased in UAendo from follicular and pregnant sheep. Ovariectomized ewes (OVEX) had substantially reduced UAendo ERbeta, but not UAendo ERalpha or OAendo ERalpha and ERbeta. In contrast, OVEX increased UA VSM ERalpha and ERbeta and decreased OA VSM ERalpha and ERbeta. Treatment with oestradiol-17beta (E2beta), but not progesterone or their combination, increased UAendo ERalpha levels. The reduced ERbeta in UAendo from OVEX ewes was reversed by E(2)beta and progesterone treatment. While ERalpha and eNOS were not elevated in any other reproductive or non-reproductive endothelia tested, ERbeta was augmented by pregnancy in uterine, mammary, placenta, and coronary artery endothelia. ERalpha and ERbeta mRNA and protein are expressed in UA endothelium with expression levels depending on the endocrine status of the animal, indicating UA endothelium is a target for oestrogen action in vivo, and that the two receptors appear to be differentially regulated in a spatial and temporal fashion with regard to the reproductive status or HRT.

Impaired KATP channel function in the fetoplacental circulation of patients with type 1 diabetes mellitus

OBJECTIVE

The increased perinatal morbidity in diabetes may be partly related to vascular dysfunction. Because potassium channels play an important role in the regulation of vascular tone, this study explores the impact of diabetes on potassium channel function in the fetoplacental vascular bed.

STUDY DESIGN

Vascular potassium channel function was investigated by ex vivo dual perfusion of isolated placental cotyledons (n = 47). Appropriate control experiments were carried out to exclude nonspecific effects.

RESULTS

Glibenclamide (KATP channel blocker) increased perfusion pressure to a maximum fetoplacental arterial pressure of 37 +/- 6 mm Hg in controls versus 15 +/- 6 mm Hg in diabetes (P < .05). 4-Aminopyridine (KV channel blocker) equally increased fetoplacental arterial pressure in controls, and in diabetes (21 +/- 4 mm Hg vs 22 +/- 2 mm Hg). Apamin and charybdotoxin (KCa channel blockers) caused a negligible rise in fetoplacental arterial pressure.

CONCLUSION

In the fetoplacental circulation, KATP channels and KV channels significantly contribute to baseline vascular tone. In diabetes, vascular KATP channel function is impaired.

Delayed normalization of uterine artery Doppler waveforms is not a benign phenomenon

OBJECTIVE

To evaluate the pregnancy outcome in patients with abnormal uterine artery Doppler flow velocity waveforms (FVW's) at 19-21 weeks, which were subsequently normal by 24-26 weeks, and to study the effect of low-dose aspirin on these waveforms.

DESIGN

The study group consisted of 49 patients who had abnormal uterine artery flow velocity waveforms (FVW's) at 19-21 weeks. These women were initially commenced on 100 mg slow-release aspirin at 20 weeks, which was discontinued at the follow-up visit, after confirming normal uterine artery Doppler FVW. The control group consisted of 730 patients with normal uterine artery Doppler waveforms at 19-21 weeks. The main outcome measures were: small for gestational age (SGA) <10th centile, pre-eclampsia, placental abruption, and perinatal mortality rate (PMR).

RESULTS

When compared with the control group, the study group had an increased risk of placental abruption (2% versus 0.27%, P = 0.05) 95% Confidence Intervals CI = 0.01-0.13), low birth weight (3087 versus 3383 gm, P = 0.0003), SGA <10th centile (32.7% versus 11.9%, P </= 0.0001 , CI = 0.14 -0.5), and PMR (2/49 versus 1/730, P < 0.0001 , CI = 0.003-0.37).

CONCLUSIONS

These findings suggest that delayed normalisation of the uterine artery Doppler waveform is not a benign phenomenon. This subgroup of patients is at increased risk of pregnancy complications, in particular SGA and placental abruption. These patients could benefit from serial ultrasound scans in the third trimester to evaluate fetal growth and well-being. Aspirin does not appear to play a major part in modifying uterine artery blood flow.

Acute effects of maternal smoking on fetal hemodynamics

OBJECTIVE

To investigate acute effects of cigarette smoking on fetal hemodynamics.

METHOD

Sixty seven women between 32nd to 40th weeks of gestation were evaluated. Maternal blood pressure and heart rate, fetal heart rate (FHR) tracing, umbilical and fetal middle cerebral arterial (MCA) color Doppler measurements were evaluated. Pre- and postsmoking results were compared with paired t-test.

RESULTS

Maternal heart rate significantly increased after smoking. Baseline FHR and FHR variability remained unchanged. The number of participants who had a reactive NST was 60 in 67 before smoking (89.5%) and decreased to 47 after smoking (70.1%) (p=0.009). There were no significant changes between maximum and minimum flow velocities, pulsatility index (PI), resistance index (RI) and systolic/diastolic flow ratio (S/D) of umbilical and middle cerebral arteries.

CONCLUSION

The nicotine load of a single cigarette may be inadequate to cause a detectable decrease in utero-placental blood flow; however, smoking prior to the FHR recording may alter the FHR reactivity.

Effects of ephedrine and phenylephrine on uterine and placental circulations and fetal outcome following fetal hypoxaemia and epidural-induced hypotension in a sheep model †

BACKGROUND

Recent studies support the use of alpha-agonists during regional anaesthesia in uncomplicated term pregnancies. We hypothesized that ephedrine and phenylephrine, administered for maternal hypotension following fetal hypoxaemia, are equal in respect of fetal outcome.

METHODS

At 117-132 days gestation, chronically instrumented, anaesthetized and mechanically ventilated ewes were randomized to receive boluses of ephedrine (n=9) or phenylephrine (n=8) for maternal epidural-induced hypotension after a period of fetal hypoxaemia. Uterine (QUtA) and placental (QUA) volume blood flows were measured with perivascular transit-time ultrasonic flow probes, and uterine (RUtA) and placental (RUA) vascular resistances were computed from volume blood flows and maternal and fetal mean arterial pressures. Uterine (PIUtA) and umbilical artery (PIUA) pulsatility indices were obtained by Doppler ultrasonography.

RESULTS

Ephedrine increased QUtA and decreased RUtA and PIUtA from a hypotensive to baseline level and had no significant effect on umbilical circulation. With phenylephrine, QUtA remained lower (P=0.011) and RUtA higher (P=0.043) than at baseline, although PIUtA decreased to baseline level. PIUA increased from baseline with phenylephrine (P=0.007), whereas QUA decreased (P=0.050). Maternal volume expansion with hydroxyethyl starch decreased RUtA significantly irrespective of the vasopressor used. There were no significant differences in fetal blood gas values or lactate concentrations between the ephedrine and phenylephrine groups.

CONCLUSIONS

Despite the more favourable effects on uterine and placental circulations of ephedrine over phenylephrine, no significant differences in fetal acid-base status or lactate concentrations were observed.

Low-molecular-weight heparin lowers the recurrence rate of preeclampsia and restores the physiological vascular changes in angiotensin-converting enzyme DD women

Data from literature report that angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism affects the recurrence of preeclampsia and that low-molecular-weight heparin (LMWH) prevents adverse outcomes in thrombophilic women. We investigated the effect of LMWH on the pregnancy outcome, on maternal blood pressure values, and on uteroplacental flow in ACE DD nonthrombophilic women with history of preeclampsia. Eighty nonthrombophilic ACE DD women were randomized in 2 groups: 41 treated with dalteparin 5000 IU/day and 39 untreated (control group). Women underwent 24-hour automated blood pressure monitoring in the preconceptional period and every 2 weeks from weeks 8 to 36 and transabdominal color flow/pulsed Doppler examination at weeks 16, 20, and 24. LMWH reduced the risk of clinical negative outcomes (74.1% reduction of preeclampsia and 77.5% reduction of fetal growth restriction) and the severity (88.3% reduction of early onset of preeclampsia and 86.4% reduction of early onset of fetal growth restriction). In treated women, the relative risk for preeclampsia was 0.26 (P=0.02), and the relative risk for fetal growth restriction was 0.14 (P<0.001). Systolic (P=0.002) and diastolic (P=0.002) blood pressures, as well as awake (P=0.04) and asleep (P=0.01) period values, and the resistance indexes of both uterine arteries (P=0.002) were lower in the treated group. LMWH reduces the recurrence of preeclampsia, of negative outcomes, and the resistance of uteroplacental flow, and also prevents maternal blood pressure increase in ACE DD homozygote women with a previous history of preeclampsia.

N-acetylcysteine restores nitric oxide-mediated effects in the fetoplacental circulation of preeclamptic patients

OBJECTIVE

Preeclampsia is associated with an imbalance between oxidants and antioxidants, resulting in reduced effects of the endothelium-derived, relaxing-factor nitric oxide (NO). Antioxidants, like N-acetylcysteine (NAC), remove reactive oxygen species, resulting in an improvement of endothelial function. We aimed to investigate the effect of NAC on the NO-pathway in the human fetoplacental circulation in preeclampsia and control pregnancies.

STUDY DESIGN

The NO-pathway was investigated by use of the NO-synthase inhibitor L-NAME in an ex vivo cotyledon perfusion model.

RESULTS

At baseline, fetoplacental arterial pressure was comparable in preeclamptic pregnancies (n=8) and control pregnancies (n=8), and increased dose-dependently after L-NAME. The maximal L-NAME-induced rise in fetoplacental arterial pressure was attenuated in preeclamptic versus control pregnancies (20.8 +/- 2.0 mm Hg vs 36.7 +/- 3.5 mm Hg, P<.05). Addition of NAC increased the L-NAME-induced rise in fetoplacental arterial pressure to 36.4 +/- 3.4 mm Hg in preeclampsia pregnancies (P<.05) and to 49.2 +/- 2.6 mm Hg in control pregnancies (P<.05).

CONCLUSION

Preeclampsia is associated with a dysfunction of the NO-pathway. N-acetylcysteine increases NO-mediated effects in the fetoplacental circulation in preeclamptic placentas as well as in healthy control placentas.

Nitric oxide donors: effects on fetoplacental blood flow

OBJECTIVE

To investigate fetal and uteroplacental blood flow after transdermal administration of glyceroltrinitrate (GTN) in pregnancies at risk for preterm delivery.

STUDY DESIGN

Twenty-five pregnant women who received GTN patches (Nitroderm TTS 10) with a dosage of 0.8 mg/h, because of risk for preterm delivery, were included in the prospective study. Doppler measurements (resistance index, RI) of the umbilical artery (UA), the middle cerebral artery (MCA) and the uterine arteries of the placental (UTA-P) and the non-placental (UTA-NP) side, with calculation of the mean-RI (UTA-mean), were performed before and after 24, 48 and 72 h of the 1st GTN application. Wilcoxon test and Holm correction were used for statistical analysis.

RESULTS

The initial RI values were in the normal range. Significant decreases of the RI of UTA-NP ( P = 0.02 ) and UTA-mean ( P = 0.03) were observed 24h after GTN application. The other RI values did not show significant changes.

CONCLUSION

Transdermal nitroglycerine used for the treatment of preterm labour does only reduce uterine vascular impedance at the non-placental side with primary higher resistance. It does not affect fetal perfusion and uterine perfusion at the placental side with normal blood flow resistance.

Comparison of accumulation and altered steroid secretion by placental tissue treated with TCDD and natural mixture of PCDDs-PCDFs

Explants of human placental tissue harvested immediately after expulsion were used to determine differences between accumulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and polychlorinated dibenzo-p-dioxin (PCDD)-polychlorinated dibenzo-p-furans (PCDF) environmental mixture, and their influence on placental steroidogenesis. Explants were cultured in vitro for 5 days in media supplemented each day with either TCDD or a mixture of PCDD-PCDF. Media were collected every day for steroid content analysis by radioimmunoassay. At 24 h after the last treatment, the tissue was frozen for further analysis of the content of TCDD or other congeners present in the mixture. Determinations of TCDD and all 17 PCDDs and PCDFs were performed using gas chromatography equipped with DB-5 MS and DB-17 capillary columns. In the control tissue, the amounts of both TCDD and mixture components were close to the limit of detection of the method. In the treated tissue, the TCDD accumulation was 94% of the total exposure to TCDD. The most toxic congeners 2,3,7,8-TCDD, 2,3,7,8-tetrachlorodibenzofuran, 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 1,2,3,7,8-pentachlorodibenzo-p-furans (PeCDF) and 2,3,4,7,8-PeCDF showed the highest accumulation, which covered >50% of the total toxic equivalents present in this mixture. During the first 3 days of exposure to TCDD there was no effect on the conversion of dehydroepiandrosterone to oestradiol, whereas on days 4 and 5 of exposure, a twofold decrease in oestradiol secretion was observed. However, a small but significant increase in oestradiol secretion was noted at all times of exposure to the PCDD-PCDF mixture. All observed changes in oestradiol secretion were not accompanied by changes in progesterone secretion after exposure to TCDD or the PCDD-PCDF mixture. In conclusion, a high accumulation of TCDD in the placental tissue resulted in a decrease in oestradiol secretion and in vivo this could result in a decrease in blood flow through the placenta. From the mixture, PeCDD and PeCDF in the higher amount accumulated in the placental tissue caused an increase in oestrogen secretion and as a consequence could activate oxytocin secretion from the pituitary and early pregnancy outcome.

Ovine feto-placental metabolism

Fetal growth depends on the transplacental nutrient supply, which, in turn, is determined partially by the consumption and production of nutrients by the uteroplacental tissues. In fetal sheep, the rates of growth and umbilical glucose uptake decline coincidently towards term in parallel with the normal prepartum rise in plasma cortisol. While cortisol is known to reduce growth in fetal sheep, its effects on the uteroplacental handling and delivery of nutrients remain unknown. Hence, this study, quantified the rates of umbilical uptake and uteroplacental consumption of nutrients in preterm fetuses infused with cortisol for 5 days to mimic the prepartum cortisol surge. Umbilical uptakes of glucose and lactate, but not oxygen, were significantly lower in cortisol- than saline-infused fetuses, irrespective of whether values were expressed as absolute or weight-specific rates. The rate of uteroplacental consumption of glucose, but not oxygen, was significantly higher in cortisol- than saline-infused animals. Absolute rates of uteroplacental lactate production were lower in cortisol-infused animals. When all data were combined, fetal plasma cortisol levels were positively correlated to uteroplacental glucose consumption and inversely related to umbilical glucose uptake. Cortisol treatment had no apparent effect on placental mRNA expression for the glucose transporters, GLUT-1 and GLUT-3. The results demonstrate that cortisol is physiological regulator of uteroplacental metabolism and nutrient delivery to the sheep fetus. These observations have important implications for fetal growth both in late gestation and during adverse intrauterine conditions, which raise fetal cortisol levels earlier in gestation.

Medications in pregnancy and lactation

Lack of information and misinformation often lead to physicians advising mothers to discontinue breastfeeding because of medication use. Also, many mothers do not adhere to their prescriptions or quit breastfeeding because of medication use. Although in both cases this cessation of breastfeeding is probably based on concern for the infant's safety, the physician may also be influenced by expediency and fear of litigation. The safest course for physicians who are treating nursing mothers is to consult reliable sources before advising discontinuation of breastfeeding. Overwhelming evidence has shown that breastfeeding is the most healthful form of nutrition for babies and should therefore be encouraged by physicians. Physicians should take the following approach to maximize safe maternal medication use for both the mother and the breastfed infant: 1. Determine if medication is necessary. 2. Choose the safest drug available, that is, one that; is safe when administered directly to infants, has a low milk:plasma ratio, has a short half-life, has a high molecular weight, has high protein binding in maternal serum, is ionized in maternal plasma, is less lipophilic. 3. Consultation with the infant's pediatrician is encouraged. 4. Advise the mother to take the medication just after she has breastfed the infant or just before the infant's longest sleep period. 5. If there is a possibility that a drug may risk the health of the infant, arrange for the monitoring of serum drug levels in the infant. Emergency physicians are often faced with the daunting task of treating a large variety of high-acuity patients, including patients who happen to be pregnant or nursing mothers. Priority, of course, needs to be given to life-saving treatment. When physicians are treating pregnant or breastfeeding patients, they need to use reliable resources to evaluate the risks and benefits of the medication for the mother and the infant. Most medications should have no effect on milk supply or on infant well-being. In most cases, treatment plans for patients should include encouragement from the emergency physician that he or she has researched the chosen medicine and that breastfeeding may safely continue.

Trophoblastic injury: new etiological and pathological concept of preeclampsia

AIM

To analyze published data related to modern insight in the etiology of preeclampsia.

METHODS

We analyzed 38 published articles on the etiology of preeclampsia. The articles were identified by a combined search of PubMed database of the National Library of Medicine, USA, by using the key words "preeclampsia" and "cause/etiology". Full-text articles were retrieved from the library of Hamamatsu University School of Medicine and Japan's library network.

RESULTS

According to the reports, vasospasm and vascular endothelial injury were two major pathological conditions of preeclampsia. They could be classified into 4 types of uteroplacental circulation failure: 1) disturbance in the circulation from the aorta to the uterine artery, 2) disturbance in the circulation of the spiral artery, 3) disturbance in the circulation of the intervillous space, and 4) disturbance in the circulation of the uterine vein reflux disorder. Major vessel bed of the uteroplacental unit consists of trophoblast, not of endothelial cells. Moreover, the trophoblast has many cellular functions, such as endothelial, immune, neural, and hormonal, resulting in production of various vasoactive substances. Thus, trophoblastic injury induced by uteroplacental circulation failure could affect and deteriorate the systemic circulation of the mother, resulting in preeclamptic symptoms.

CONCLUSION

The development of preeclampsia could be envisioned as a series of events from uteroplacental circulation failure to trophoblastic injury to vascular endothelial injury or vasospasm. The concept of "trophoblastic injury attributable to the uteroplacental circulation failure" can be a signpost for further investigations into the etiology of preeclampsia and type-specific treatment of preeclampsia.

Vasoactive effects of erythropoietin on human placental blood vessels in vitro

OBJECTIVE

The aim of this study was to investigate the direct effect of erythropoietin on human placental vessels.

STUDY DESIGN

Placental vessel rings (n = 8 for each group) from uncomplicated pregnancies were exposed to recombinant human erythropoietin (10-300 IU/mL) in an isometric myograph. One-way analysis of variance with the Bonferroni posttest was used to evaluate significant levels of differences.

RESULTS

Recombinant human erythropoietin evoked reproducible contractions on the vessel rings in a dose-dependent way, which were marked significantly more on veins than on arteries. These contractile responses were not changed by captopril (10(-5) mol/L) but were blunted significantly by losartan (10(-5) mol/L).

CONCLUSION

We concluded that recombinant human erythropoietin exerts a direct contractile effect on human placental vessels, angiotensin II type 1 receptors are needed to mediate these responses, and erythropoietin might participate in one of the humoral mechanisms that are involved in the control of the human placental vascular bed and also in the pathogenesis of intrauterine growth restriction and preeclampsia.

Maternal dexamethasone increases endothelin-1 sensitivity and endothelin a receptor expression in ovine foetal placental arteries

Despite National Institutes of Health recommendations to administer antenatal steroids as a single course to women threatening preterm delivery, repeated treatments are often given. We investigated effects of repeated dexamethasone (DM) administered to the ewe on small maternal and foetal placental arteries. We hypothesized that DM would increase responsiveness to endothelin-1 (ET-1) and norepinephrine (NE) and that foetal arteries would react differently to ET-1 and NE compared to maternal arteries. Ewes received three treatments beginning at 103, 110, and 117 days of gestation (dGA). Each treatment consisted of four IM injections of 2mg DM or saline at 12-h intervals. At 119 dGA, in vitro functional studies were performed using Mulvany wire myography and endothelin receptor (ETR) expression was quantified using real-time RTPCR and receptor ligand autoradiography. Foetal placental arteries demonstrated greater maximal contractility to ET-1 and lesser maximal contractility to NE compared to maternal arteries. DM increased the maximal contraction elicited by ET-1 and NE in foetal but not maternal placental arteries. DM also increased the abundance of type-A ETR but not type-B ETR mRNA in foetal but not maternal placental arteries. However, within the whole placentome, DM increased the abundance of type-B ETR and decreased type-A ETR mRNA, which was confirmed by similar changes in ETR binding specifically within the labyrinth region. In summary, repeated DM treatment results in agonist and vascular bed specific responses within the placenta.

Application of electric field stimulation for investigations of human placental blood vessels

OBJECTIVE

To test electric field stimulation on human placental vessels.

METHODS

The effects of electric field stimulation on placental vessels were examined in an isometric myograph.

RESULTS

Electric field stimulation induced contractions in human placental blood vessels in vitro under isometric conditions when bubbling carbogen through the organ bath. After reaching half-maximal contractions, the vessel rings showed spontaneous relaxation. Pretreatment with verapamil (10(-6) mol/L) or nickel (Ni(2+)) (2 mmol/L) inhibited the contractions to a magnitude of 63.81% +/- 7.69% and 88.36% +/- 12.17% (mean +/- standard error of the mean), respectively. In calcium (Ca(2+))-free medium after combined cyclopiazonic acid (10(-5) mol/L) and Ni(2+) treatment, it was not possible to elicit contractions with electric field stimulation. Bubbling through physiologic in utero hypoxic gases enhanced the contractile responses of the human placental vessel rings to electric field stimulation. The spontaneous relaxation of the veins was not altered, but those of the arteries were reduced to zero. Testing the same gases on mesenteric arteries of rats had an opposite effect concerning contractility. Sodium nitrite decreased the contractions of the placental vessel rings, but the efficacy was decreased by the in utero gases.

CONCLUSION

Electric field stimulation has a direct, non-neurogenic contractile effect on isolated placental vessels, which mainly depends on the influx of extracellular Ca(2+) and on a mechanism independent of intracellular Ca(2+) concentration elevation. Physiologic hypoxia has a stimulatory effect on the contractility of human placental vessels, therefore in utero gases should be used instead of carbogen gas; and electric field stimulation is a suitable method for the investigation of the direct effects of pharmacologic agents on human placental vessels.

Misoprostol and dinoprostone therapy for labor induction: a Doppler comparison of uterine and fetal hemodynamic effects

OBJECTIVE

To compare the effect of misoprostol (PGE(1)) versus dinoprostone (PGE(2)) on blood flow in uteroplacental circulation during labor induction.

STUDY DESIGN

Eighty-four women with indications for induction of labor were assigned to receive either misoprostol 50 microg per vagina every 4 h as needed or 0.5 mg doses of dinoprostone given intra-cervically every 6 h by means of a randomization table generated by computer. Doppler velocimetry of umbilical, uterine and arcuate arteries was performed immediately before and 2-3 h after the administration of misoprostol or dinoprostone. The SAS system was used to perform statistical analysis.

RESULTS

There were no significant changes of pulsatility index (PI), resistance index (RI) and systolic/diastolic (S/D) ratio in umbilical arteries after both prostaglandin compounds. Vaginal application of misoprostol significantly increased all ratios in arcuate artery and S/D ratio in uterine artery. Intra-cervically dinoprostone significantly increased PI, RI and S/D ratio in arcuate and uterine arteries.

CONCLUSIONS

Our results indicate that vaginal misoprostol and cervical dinoprostone administration increases uteroplacental resistance but does not affect umbilical blood flow. Misoprostol would be as safe and effective agent as dinoprostone for cervical ripening and labor induction.

Changes in umbilical artery flow velocity waveforms following maternal administration of betamethasone

In a retrospective cohort study we have previously shown that administration of betamethasone to women with a pregnancy complicated by absent end-diastolic flow in the umbilical artery (UA) is associated with altered UA flow velocity waveforms. To examine this phenomenon further we undertook a prospective study of 30 similar singleton pregnancies. Umbilical artery FVWs were recorded before and after betamethasone administration using real-time pulsed wave colour flow Doppler. The results of this prospective cohort were similar to those of the retrospective study allowing pooling of the data. Of the 55 total pregnancies with umbilical artery AEDF studied betamethasone administration was associated with the return of end-diastolic flow in 39 (71 per cent; 95 per centCI: 59-83 per cent). The median (range) duration of this change was 3 (1-10) days. There is no evidence that this change has either a beneficial or detrimental effect on foetal health. Administration of betamethasone to women with a pregnancy complicated by umbilical artery AEDF is associated with the transient return of end-diastolic flow in most cases. While the mechanisms underlying this effect are yet to be fully elucidated it has implications for foetal surveillance in these high-risk pregnancies.

[Adrenomedullin in pregnancy]

In this study, we used the animal model of preeclampsia. The blood pressure in animals receiving L-NAME at 25 mg/day were significantly higher compared to that of rats receiving saline solution only. In addition, L-NAME treated rats showed a high fetal mortality as compared with intact rats. Also, we demonstrated infusion of AM reverse the hypertension and decrease in pup mortality induced by L-NAME during pregnancy. We showed that the AM mRNA levels predominantly exists in a high level in the placenta, uterus and ovary as compared with other tissues. These evidences suggest that AM may have a possible important role during pregnancy. In conclusion, the present study suggest that L-NAME-induced elevated blood pressure and increased fetal mortality can be reversed by low dose of AM. Thus AM may play an important role in the regulation of blood pressure, the blood supply to the utero-placental unit and fetal development.

Carbon monoxide decreases perfusion pressure in isolated human placenta

Carbon monoxide (CO) is one of the metabolites formed via heme oxidation catalysed by the enzyme heme oxygenase (HO). Endogenous formation of CO, mediated by HO, has been noted in both placental and umbilical vessels. In blood vessels from different mammalian sources, it has been proposed that the vasodilator effect of CO is mediated via stimulation of soluble guanylyl cyclase (sGC) and consequent increased cGMP formation. The purpose of the present study was to determine the effect of exogenous CO on placental cotyledon perfusion pressure and to determine the role of sGC in the CO-induced decrease of perfusion pressure using the in vitro human placental perfusion preparation. A thromboxane A2 mimetic (U46619) was added to the foetal perfusion medium to constrict the placental blood vessels. Carbon monoxide was added to the foetal perfusion medium in increasing concentrations to determine its effect on placental perfusion pressure. Carbon monoxide produced a concentration-dependent decrease in placental perfusion pressure. The addition of ODQ, a sGC inhibitor, attenuated the CO-induced decrease in placental perfusion pressure, while addition of YC-1, an activator of sGC, augmented the CO-induced decrease in placental perfusion pressure. The data indicate that CO causes vasorelaxation of placental resistance blood vessels, in large part, via activation of sGC.

[Influence of labetalol on the resistance of human fetoplacental vessels in perfusion in vitro]

OBJECTIVES

The main unfavourable effects observed in gestosis include: increased vascular peripheral resistance and increased blood pressure with a defective uteroplacental flow. The above mentioned changes may result from disorders in prostacyclin PGI2/thromboxane A2 balance.

DESIGN

The aim of the studies presented was to compare the effects of, labetalol on the fetal vascular resistance induced by U 46,619--stable analogue of thromboxane A2 an experimental bilateral perfusion of the human placental lobule.

MATERIALS AND METHODS

The researchers used the experimental model described by Schneider. 12 perfusions of the human placental lobules were performed. The control and labetalol groups consisted in 6 placental lobule perfusions lasting 120 min each. Having obtained constant increase in perfusion pressure from the 60th min of the experiment, labetalol was administered along with thromboxane A2 analogue into the fetal circulation. The perfusion pressure was steadily recorded on the kymograph tape.

RESULTS

The stable increase of perfusion pressure was observed from the 60th minute with the average of 185% of the initial pressure. This value represented the reference standard in the second stage of the studies in which the effects of labetalol on the experimentally increased perfusion pressure was evaluated.

CONCLUSIONS

Labetalol did not significantly affect the hemodynamics of fetoplacental vessels.

Changes in fetoplacental vessel flow velocity waveforms following maternal administration of betamethasone

OBJECTIVE

To determine the timing of the onset of the umbilical artery flow velocity waveform changes following maternal administration of betamethasone in pregnancies complicated by umbilical artery absent end-diastolic flow, and to explore whether these changes are associated with flow velocity waveform changes in other fetoplacental vessels.

SUBJECTS AND METHODS

This was a prospective study of 12 women with pregnancies complicated by umbilical artery absent end-diastolic flow. Flow velocity waveforms were recorded from the umbilical artery, fetal middle cerebral artery, renal artery, aorta and ductus venosus, before and after maternal betamethasone administration, using real-time pulsed wave Doppler.

RESULTS

In all 12 pregnancies, the administration of maternal betamethasone was followed by the return of end-diastolic flow within 24 h. End-diastolic flow was first observed at 4 h and was present in all women studied at 8 h. In addition, there was a statistically significant decrease in the pulsatility index in the fetal aorta at 8 h and the middle cerebral artery at 24 h. No change was observed in the ductus venosus or the renal artery flow velocity waveforms.

CONCLUSION

The findings suggest that, in pregnancies complicated by absent end-diastolic flow in the umbilical artery, maternally administered betamethasone induces a return in umbilical artery end-diastolic flow as early as 4 h, along with widespread vasodilatation throughout the fetoplacental vasculature.

A long-term transdermal nitric oxide donor improves uteroplacental circulation in women with preeclampsia

OBJECTIVE

To determine the effects of long-term transdermal administration (range, 4-30 days; mean +/- SD, 11.1+/-7.2 days) of isosorbide dinitrate, a nitric oxide donor, in preeclamptic women.

METHODS

We studied uterine and fetoplacental circulation of 12 preeclamptic women with oligohydramnios and an elevated pulsatility index in the uterine arteries.

RESULTS

Transdermal isosorbide dinitrate significantly suppressed the blood pressure of patients. Pulsed Doppler ultrasonography revealed that the average pulsatility index in the uterine arteries was significantly reduced by treatment with isosorbide dinitrate (P < .003). The average pulsatility index in the umbilical artery was also significantly reduced (P < .004). Furthermore, the size of the amniotic fluid pocket increased approximately 4-fold by treatment with isosorbide dinitrate.

CONCLUSIONS

Long-term transdermal administration of isosorbide dinitrate improves fetoplacental circulation and may be effective therapy for avoiding maternal hypertension and oligohydramnios in some preeclamptic women.

The effect of methyldopa treatment on uterine, umblical and fetal middle cerebral artery blood flows in preeclamptic patients

The purpose of this study was to evaluate the efficacy of methyldopa in the treatment of preeclamptic patients. This study was performed on 24 preeclamptic women who were in between 25-36 weeks of gestational age. 24 healthy pregnant women were taken as control group. Before starting treatment, 24 preeclamptic patients were examined with Doppler ultrasound. Pulsatility index, resistance index, systolic/diastolic ratio of uterine, umblical and fetal middle cerebral arteries were measured. Preeclamptic patients were treated with totally 1 g methyldopa per day. After 7 d, patients were reexamined with Doppler ultrasound. The effect of methyldopa on uterine, umblical and fetal middle cerebral artery blood flows were detected. Only one control with Doppler ultrasound was done to the healthy pregnant women. Before methyldopa treatment to the preeclamptic women, pulsatility index (PI), resistance index (RI) and systolic/diastolic ratio (S/D) on uterine and umblical arteries were significantly higher than the control group. However, fetal middle cerebral artery (MCA) values were significantly lower than the control group. When Doppler results of preeclamptic patients before and after the methyldopa treatment were compared, no significant differences in terms of Pulsatility Index, Resistance IndexI and S/D ratio of umblical and fetal middle cerebral arteries were found. However, the results of uterine artery were significantly lower after the treatment in preeclamptic patients. Treatment with methyldopa lowered the uterine artery resistance in preeclamptic patients but did not effect the resistance of umblical and fetal middle cerebral artery.

Short-term effects of glucocorticoids in the human fetal-placental circulation in vitro

A number of studies demonstrate that both long-term and short-term exposure to glucocorticoids alters vascular function. We have examined whether the short-term administration of glucocorticoids into the human fetal-placental circulation affects placental arterial pressure and alters vascular responses to vasoconstrictive and vasodilator agents. Single lobules of term human placentae were bilaterally perfused in vitro with Krebs' solution (maternal and fetal, 5 ml/min Krebs, 95% O2, 5% CO2, 37 C, pH 7.3), and changes in fetal-placental arterial perfusion pressure were measured. Dexamethasone (100 nM) infusion for 1 h into the fetal-placental circulation caused a significant decrease in basal arterial pressure (n = 19, t test, P < 0.05). Continuous dexamethasone infusion (100 nM) did not alter vasoconstrictive responses to PGF(2alpha) (0.5-120 pM, n = 12, ANOVA, P > 0.05) or potassium chloride (5-600 mM, n = 12, ANOVA, P > 0.05) or vasodilator responses to CRH (53-7400 pM, n = 13, ANOVA, P > 0.05). However when fetal-placental vessels were submaximally preconstricted and then infused with dexamethasone alone (40 nM-10 microM), there was a dose-dependent decrease in arterial pressure (n = 8). Dexamethasone-induced dilation was not inhibited by blocking nitric oxide synthase or cyclo-oxygenase activity. These data suggest that dexamethasone can cause dilation in the fetal-placental circulation, possibly via an endothelium-independent pathway.