Vasoactive effects of 8-epi-prostaglandin F(2alpha)in isolated human placental conduit and resistance blood vessels in vitro

The effects of 8-epi-prostaglandin F(2alpha)(8-epi-PGF(2alpha)) and the thromboxane A(2)-mimetic U46619 were examined on isolated human fetal placental arteries obtained from normal pregnancies and from those complicated by pre-eclampsia. The effects of these agents were examined on both conduit and resistance arteries. 8-epi-PGF(2alpha)was found to be markedly less potent than U46619 in constricting both size vessels. Vasoconstrictor EC(50)s for 8-epi PGF(2alpha)were 4.10x10(-7) m (2.02-8.35x10(-7) m) (mean, 95 per cent CI and 2.05x10(-6) m (0.43-9.89 x10(-6) m) in conduit and resistance arteries, respectively. The maximum vasoconstriction produced by 8-epi-PGF(2alpha)(112+/-17 per cent), (relative to maximum KCl induced vasoconstriction) in conduit vessels was significantly less than that caused by U46619 (152+/-20 per cent). In resistance vessels the maximum vasoconstrictor effects to 8-epi-PGF(2alpha)(208+/-10 per cent) and U46619 (201+/-19 per cent) were similar, and in both cases significantly greater than the maximal effects seen in conduit vessels. U46619 displayed a similar vasoconstrictor potency in both conduit (EC(50)=1.21x10(-9) m, 0.58-2.51x10(-9) m) and resistance arteries [EC(50)=5.95x10(-9) m, (0.81-43.60x10(-9) m] as was found for 8-epi PGF(2alpha). 8-epi-PGF(2alpha)was equipotent in resistance arteries obtained from women with severely pre-eclamptic pregnancies (EC(50)=1.25x10(-6) m, 0.25-6.17x10(-6) m) compared with normotensive controls. However, the maximum vasoconstrictor effect induced by 8-epi-PGF(2alpha)in placental resistance arteries was significantly reduced (99+/-20 per cent) in vessels obtained from severely pre-eclamptic compared with normal pregnancies. These results indicate that 8-epi-PGF(2alpha)displays differential vasoconstrictor activity in the fetal-placental vasculature. Furthermore the vasoconstrictor effects of 8-epi-PGF(2alpha)are reduced in pre-eclampsia, the effect being selective to placental resistance vessels. This reduction may occur as a result of more serious disturbances in the placental microcirculation with the disease process in pre-eclampsia.

Effects of nitrovasodilators on the human fetal-placental circulation in vitro

This study examines the vasorelaxation of isolated human placental chorionic plate arteries and the perfused fetal-placental vasculature, in vitro, to a variety of nitrovasodilator compounds including glyceryl trinitrate (GTN) sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine (SNAP), S-nitroso-N-glutathione (SNG) and NaNO(2). The effects of these compounds were also examined under conditions of high (>450 mmHg) and low oxygen (<50 mmHg) tension. In a separate series of experiments the effects of GTN and NaNO(2)were further investigated with addition of the antioxidants cysteine (100 microm), glutathione (100 microm) or superoxide dismutase (SOD) (30 I.U./ml). The order of nitrovasodilator potency, when added directly to isolated fetal vessels was GTN=SNP>SNAP=SNG>NaNO(2). The order under low oxygen tension was similar, GTN=SNP>SNG= SNAP>or=NaNO(2). SNG ( approximately fourfold) and NaNO(2)( approximately 50-fold) were significantly more potent under low oxygen conditions. Cysteine, glutathione and SOD were without effect on GTN induced vasodilatation. However, all three agents significantly enhanced (six- to ninefold) the effects of NaNO(2)under similar conditions. When infused directly into the fetal-placental circulation during in vitro perfusion experiments the order of potency was GTN>SNP>or=SNG>or=SNAP>or=NaNO(2). When the nitrovasodilators were infused indirectly via the maternal intervillous space the order of potency was GTN>or=SNP>or=NaNO(2)>or=SNAP=SNG. Our observations suggest that there are important differences in the action of different classes of nitrovasodilator compounds on the fetal-placental circulation. The changes observed with SNG and NaNO(2)may be influenced by levels of tissue oxygenation.

Fetal placental vascular responses to corticotropin-releasing hormone in vitro. Effects of variation in oxygen tension

In this study, using the human placenta perfused in vitro with Krebs' bicarbonate solution, we have examined the effects of changes in oxygen tension on the vasoreactivity of fetal placental blood vessels to corticotropin releasing hormone (CRH). Vasodilatory responses to human synthetic CRH were measured during sub-maximal vasoconstriction of the fetal placental circulation with prostaglandin F(2alpha)(PGF(2alpha)) (1-100 micrometer). Decreases in fetal placental arterial perfusion pressure (FAP) were obtained with CRH under conditions of high oxygen or low oxygen tension, >/=450 mmHg and </=50 mmHg, respectively. Secretion of CRH into the maternal and fetal placental circulations was measured during changes in oxygen tension in normal placentae and placentae from abnormal pregnancies complicated by pre-eclampsia. The change from high to low oxygen perfusion resulted in a small increase in the basal perfusion pressure (21+/-3.6 to 28.3+/-2.6 mmHg; (P</= 0.001, Student's paired t -test). During high oxygen perfusion, CRH (0. 3-3000 p m) caused a concentration dependent reduction of the PGF(2alpha)induced increase in FAP. However, during low oxygen perfusion, the vasodilatory effects of CRH were completely inhibited (P</= 0.05, regression analysis, ANOVA). The effect of the NO synthase inhibitor l -nitro-omega-arginine methyl ester (l -NAME, 1-100 micrometer), on basal FAP during high and low oxygen conditions was also established. Low oxygen perfusion significantly attenuated l -NAME-induced increases in perfusion pressure (P</= 0.05, regression analysis, ANOVA). Low oxygen perfusion was associated with an increase in CRH secretion into the maternal but not fetal circulation. CRH release into either the maternal or fetal circulations of abnormal placentae were not significantly different from normal controls. In conclusion CRH-induced vasodilatation of the fetal placental vasculature in vitro is inhibited during low oxygen perfusion. This effect may be related to reduced NO production. Reduced CRH induced vasodilation is associated with increased secretion of the CRH into the maternal but not fetal circulation.

Analysis of mid-trimester corticotrophin-releasing hormone and alpha-fetoprotein concentrations for predicting pre-eclampsia

The aims of this study were firstly to examine if corticotrophin-releasing hormone (CRH) concentrations in maternal plasma were significantly elevated in Chinese pregnancies complicated by pre-eclampsia, secondly to assess if this elevation could be detected in the mid-trimester before onset of clinical signs of the disease, and thirdly to evaluate the performance of using maternal CRH and/or alpha-fetoprotein (AFP) concentrations in the mid-trimester for prediction of pre-eclampsia. The first part of this study was tested in a cohort of 39 subjects. The CRH concentrations were significantly elevated in pregnant women complicated by pre-eclampsia. The second and third parts of the study involved a different cohort of 1021 subjects. Both CRH and AFP concentrations in the mid-trimester were significantly elevated in those who subsequently developed pre-eclampsia. However, when used for prediction of pre-eclampsia, neither the CRH nor AFP concentrations alone in the mid-trimester had strong predictive value. Although the combination of both tests improved the detection rate compared to the use of CRH alone, the small increase in the likelihood ratio from 1.9 to 2.6 did not suggest that the combination would be of great clinical value.

Can preclinical medical students be integrated into the continuing medical education process by instructing prehospital care providers?

OBJECTIVE

To develop a model introducing medical students (MS) to the continuing medical education (CME) process while simultaneously developing a curriculum to enhance the relevant surgical anatomy knowledge base of the advanced prehospital care provider.

METHODS

A CME curriculum for teaching human anatomy was developed and approved by the governing state agencies for prehospital education. The curriculum focused on structures relevant to the prehospital care of the trauma patient in a case based format using common scenarios presented by surgery and emergency medicine faculty. Five year-one medical students who completed gross anatomy served as teaching staff and were given a structures list one week prior to the CME course. Human cadavers were prosected by the medical students prior to the CME program under the guidance of the surgical faculty. Course attendees and medical student staff were anonymously surveyed at the end of the program (rating scale 1 = low to 5 = high). Prehospital providers were given a multiple-choice posttest and surveyed at 3 months after the course with regard to applicability to their current practice. Data are means +/- SD.

RESULTS

Nineteen licensed practicing paramedics attended the course. All of the paramedics scored above the 85% passing cutoff on the posttest (95. 6% +/- 6.2%). Instructor qualities were rated highly (4.62 +/- 0.49) with no instructor rating less than a 3. MS believed themselves well prepared to teach (5 +/- 0), and spent 2 +/- 0.81 hours in preparation. They were only infrequently faced with questions they were not well prepared to answer (1.25 +/- 0.5) and would uniformly participate in CME offerings in the future (5 +/- 0). The CME program improved the MS view of CME (3 +/- 0), prehospital education (3 +/- 1.4), and the surgeon as educator (3.25 +/- 1.5). At 3 months, the paramedics felt that the CME program significantly impacted the care they rendered (4.37 +/- 0.76), and improved their understanding of injury complexes (4.53 +/- 0.61), and resuscitation (4.26 +/- 0. 73). The cadaver course was uniformly recommended to coworkers (5 +/- 0).

CONCLUSIONS

This model provided prehospital care providers direct contact with clinically relevant human anatomy, enhanced their understanding of pertinent anatomy, and positively impacted their patient care. MS were introduced to the CME process and found it to be one with which they would become reinvolved. Furthermore, the MS felt prepared to present human anatomy, met the expectations of the course attendees, improved their understanding of prehospital education, and positively altered their perception of the surgeon as an educator. This process holds promise as both a model for prehospital education and as a tool for integrating MS into the role of allied health educator early in their career.

Symptoms during normal pregnancy: a prospective controlled study

Symptoms of normal pregnancy have received scant attention in the literature and what is reported is largely unsubstantiated. Yet this is an important aspect of antenatal counselling and care which deserves further investigation if symptoms are to be interpreted correctly. Accordingly, we conducted a prospective controlled study of symptoms during normal pregnancy in both primigravidas and multigravidas. A total of 38 symptoms occurred with a significantly different frequency (mainly increased) in the pregnant subjects in the third trimester compared with the controls. Of these a mean of 24.2 symptoms was experienced by each pregnant woman, double that (mean, 11.2) experienced by healthy nonpregnant controls. The 5 symptoms reported most frequently by the pregnant subjects were frequency of micturition, fatigue, pelvic pressure, insomnia and lower backache. However, a wide range of symptoms involving most body systems were reported. This study has established that symptoms of pregnancy are more numerous than mentioned in current obstetric texts and that they can be attributed to the effects of pregnancy. The third trimester is associated with the greatest number of symptoms and there is a marked decline in their number after delivery.

U46619-mediated vasoconstriction of the fetal placental vasculature in vitro in normal and hypertensive pregnancies

OBJECTIVES

To measure in-vitro responses to the thromboxane A2 (TxA2) mimetic U46619 in the fetal placental vasculature of human placentae from normotensive women and those with pre-eclampsia. Furthermore, to compare fetal vascular responses to endothelin-1,5-hydroxytryptamine, potassium chloride (KCl) and prostacyclin (PGI2) in placentae from normal or pre-eclamptic pregnancies.

METHODS

Single placental lobules of intact placentae were bilaterally perfused in situ (fetal and maternal) with constant flows of Krebs' solution. Changes in fetal arterial perfusion pressure during intra-arterial infusion of vasoactive agents were recorded. Fetal placental vasoconstrictor concentration response curves were obtained to U46619 (0.01-300 nmol/l), endothelin-1 (0.4-160 nmol/l), KCl (3-300 mmol/l) and 5-hydroxytryptamine (0.03-30 mumol/l). In addition, vasodilator concentration response curves were obtained for PGI2 (1.2-350 nmol/l) in the fetal placental circulation during submaximal increases in perfusion pressure with prostaglandin F2 alpha (PGF2 alpha; 0.7-2.0 mumol/l).

RESULTS

The maximum increase in perfusion pressure caused by U46619 in placentae from normotensive women was 194 +/- 25 mmHg. The maximum response to U46619 was significantly reduced in the placentae from women with pre-eclampsia (104 +/- 21 mmHg). In contrast, there were no differences in constrictor responses to endothelin-1,5-hydroxytryptamine and KCl, or in dilator responses to PGI2 in placentae obtained from either normotensive women or those with pre-eclampsia.

CONCLUSION

TxA2 receptor-mediated vasoconstriction is reduced in the fetal vasculature of placentae from women with pre-eclampsia, possibly to compensate for the increased levels of TxA2 seen in these conditions.

Thyrotoxic periodic paralysis in a Jamaican male

Thyrotoxic periodic paralysis is a rare endocrine disorder most prevalent among individuals of Asian descent that presents as proximal muscle weakness, hypokalemia, and signs of hyperthyroidism. We present the case report of a patient with previously undiagnosed hyperthyroidism, protracted muscle weakness with transient exacerbations, and nocturnal onset of periodic paralysis affecting the upper and lower limbs.

Vasodilator actions of urocortin and related peptides in the human perfused placenta in vitro

Urocortin, is a recently isolated peptide belonging to the CRH family that binds with high affinity to the CRH2 receptor. Like CRH, urocortin causes hypotension in the rat, but its vasoactive actions have not yet been studied in the human. We have compared the vasoactive properties of urocortin, CRH, and urotensin-1 in the human fetal placental vasculature in vitro. Single placental lobules were bilaterally perfused (maternal and fetal sides, 5 mL/min each; 95% O2-5% CO2; 37 C), and changes in fetal arterial perfusion pressure were recorded. Submaximal vasoconstriction was induced by PGF2alpha (4+/-0.7 micromol/L), which increased perfusion pressure from 19.6+/-1.4 to 100.7+/-3.1 mm Hg (n=38; P < 0.001). Subsequent fetal arterial infusion of urocortin (0.001-1 nmol/L) caused concentration-dependent vasodilatation. Urocortin was equipotent with urotensin-1 and 25 times more potent than CRH in causing vasodilatation. Nevertheless, the maximum vasodilator responses to each of the peptides were similar (P > 0.05). The CRH receptor antagonist, alpha-helical CRH-(9-41) (0.2 nmol/L) significantly attenuated the vasodilatation produced by urocortin, urotensin-1, and CRH (P < 0.05). These results indicate a possible physiological role for urocortin in the modulation of human fetal placental vascular tone by activation of CRH2-like receptors.

Arterial reactivity is enhanced in genetic males taking high dose estrogens

OBJECTIVES

We sought to assess whether high dose estrogen treatment is associated with enhanced arterial reactivity in genetic males.

BACKGROUND

Although estrogens have been shown to enhance arterial reactivity in women, and are thereby thought to confer cardiovascular benefit, the vascular effects of long-term estrogen therapy in genetic males is unknown.

METHODS

We studied the arterial physiology of 30 genetic males--15 male to female transsexuals receiving long-term high dose estrogen therapy and 15 healthy male control subjects matched for age, smoking history and vessel size. Using external vascular ultrasound, brachial artery diameter was measured at rest, after flow increase (causing endothelium-dependent dilation [EDD]) and after nitroglycerin (GTN), an endothelium-independent dilator. Blood pressure, cholesterol and testosterone levels were also measured in each subject.

RESULTS

Total testosterone and free testosterone index levels were lower in the transsexuals compared with the control subjects (p < 0.001). In contrast, EDD was significantly higher in the transsexuals than in the control males (mean [+/-SD] 7.1 +/- 3.1% vs. 3.2 +/- 2.8%, p = 0.001), as was the GTN response (21.2 +/- 6.7% vs. 14.6 +/- 3.3%, p = 0.002). Total and high density lipoprotein cholesterol, blood pressure levels and baseline vessel size were similar in the two groups. On multivariate analysis, enhanced EDD was associated independently with estrogen therapy (p = 0.02) and with low total cholesterol (p = 0.04). An enhanced GTN response was also significantly associated with estrogen therapy (p = 0.03).

CONCLUSIONS

Long-term treatment with high dose estrogens is associated with enhanced arterial reactivity in genetic males, which may be due to the effects of estrogen excess or androgen deprivation, or both.

Effects of Bufo marinus skin toxins on human fetal extracorporeal blood vessels

The effects of extracts of Bufo marinus toad skin toxin on human isolated umbilical arterial rings and the fetal vessels of perfused placentae were examined and compared with those of ouabain, an inhibitor of Na+/K(+)-ATPase. Umbilical artery rings and fetal vessels of the perfused placenta responded to extracts, or ouabain, with constriction which persisted after the removal of each agent. Extraction of the skin, using various solvents, revealed that the umbilical artery constriction was due mainly to the effects of water-soluble, polar compounds. Fractionation of a water extract and bioassay on the rat isolated aorta revealed maximum vasoconstrictor activity in a low mol. wt fraction. During Na+/K(+)-ATPase inactivation in the fetal circulation of the human placenta, by perfusion with K(+)-free Kreb's solution, reactivation of the enzyme by K+ infusion caused vasodilatation. This effect was inhibited both by water extracts of load skin and by ouabain. Thus, properties of some of the endogenous compounds in B. marinus skin resemble those of ouabain, by causing persistent constriction of human fetal blood vessels. A component of the vasoconstrictor response probably results from inhibition of vascular smooth muscle Na+/K(+)-ATPase, but it is likely that a contribution is also made by additional vasoconstrictor substances contained in B. marinus toxin.

The effects of chronic high dose androgen or estrogen treatment on the human prostate [corrected]

Prostate development and disease are androgen dependent. However, the nature of hormonal effects on the prostate of healthy young men is not clear. We, therefore, measured prostate size in males chronically exposed to high doses of androgens (AS; habitual anabolic steroid abusers; n = 15) or estrogens (E; male to female transsexuals; n = 11) and compared the results with those in age-matched healthy eugonadal men without known prostate disorders. Prostate size was measured by planimetric ultrasound as cross-sectional areas and maximal dimensions in three orthogonal dimensions with a 7.5-megahertz B-mode sector scanner biplane in a transrectal transducer at 2.5 mm steps from the base to the apex of prostate. Total prostate volume (TPV) was reconstructed from planimetric sections, central prostate volume (CPV) was calculated by the ellipsoidal formula from the appropriate three maximum dimensions, and peripheral prostate volume was determined by the difference between TPV and CPV. Compared with age-matched controls, TPV was normal (-2%) in AS (P = 0.752) and reduced by 31% in E (P = 0.002), whereas CPV was increased by 20% in AS (P = 0.002) and reduced by 46% in E (P = 0.002), and the ratio of CPV/peripheral prostate volume was increased by 77% in AS (P < 0.001) and decreased by 33% in E (P = 0.047). Blood sex hormone-binding globulin was elevated by nearly 500% in E (P < 0.001), but was reduced by 47% in AS (P = 0.003). Prostate-specific antigen was normal (-6%) in AS (P = 0.799) and decreased by 86% in E (P = 0.002). Prostatic acid phosphatase was increased by 26% in AS (P = 0.007), but was unchanged (-28%) in E (P = 0.106). Total and free testosterone levels were reduced to castrate levels in E, whereas LH, FSH, and total testosterone levels were significantly reduced in AS. We conclude that in the human prostate of young men, CPV is more hormonally sensitive than TPV, and during high dose treatment, CPV is preferentially increased by chronic androgen treatment and decreased by chronic estrogen treatment. The reduction of TPV by estrogens was less than expected if solely attributable to inhibition of endogenous gonadotropin and testosterone secretion, suggesting that estrogens also have a positive effect on the normal human prostate. The reversibility and long term significance of androgen-induced stimulation of CPV and, in particular, its relationship to the onset and severity of benign prostatic hyperplasia remain to be clarified.

Actions of magnesium, nifedipine and clonidine on the fetal vasculature of the human placenta

The anticonvulsant magnesium and the antihypertensives clonidine and nifedipine are extensively used for the clinical treatment of preeclampsia and eclampsia. Little, however, is known about the possible effects of these agents on human fetal-placental vascular resistance. We therefore examined the actions of these agents on the human fetal placental vascular bed in vitro relating the concentrations causing any vasoactive effects to the maternal blood levels attained during treatment. Placentas (n = 24) were obtained within 20 minutes of delivery from women (aged 30.2 +/- 0.9 years). In each a placental lobule was bilaterally perfused with Krebs' solution (5 mL/minute, 37 degrees C, 95% O2, 5% CO2) and fetal arterial inflow pressure (FAP) monitored. Submaximal vasoconstriction of the fetal vascular bed was induced by continuous infusion of prostaglandin F2 alpha (4.2 +/- 0.5 microM) which increased FAP from 25.9 +/- 3.9 to 95.1 +/- 6.2 mm Hg. Using a group of placentas for each drug, the effects of MgCl2, nifedipine and clonidine, were examined. Magnesium (0.3-100 mM) (n = 4) dilated the placental fetal circulation with an IC50 of 8.1 mM and a maximal response of 89.7 +/- 3.6% (n = 4). This effect of Mg2+ was not changed during concomitant infusion of the cyclo-oxygenase inhibitor, indomethacin (3 microM). Nifedipine (3-10,000 nM) also produced vasodilatation (maximum response 42 +/- 9%, n = 5). Clonidine (3-1,000 nM) caused no significant change (p < 0.05 n = 5) in vascular resistance (maximum response 11.2-5.7%) relaxation), when compared to controls. Thus in concentrations likely to be therapeutically present in maternal blood, magnesium causes a greater degree of placental fetal vasodilatation than does nifedipine, whereas clonidine is unlikely to have any effect on fetal placental vascular resistance.

Effects of variation in oxygen tension on responses of the human fetoplacental vasculature to vasoactive agents in vitro

The human placenta perfused in vitro with Krebs' solution has been used to examine the effects of low oxygen tension on the vasoreactivity of the fetal placental vessels to several vasodilator and vasocontrictor autacoids. Increases in fetal arterial perfusion pressure (FAP) produced by endothelin-1 (ET-1, human), the thromboxane A2-mimetic U46619, 5-hydroxytryptamine (5-HT), angiotensin II (A II) and bradykinin (BK) were examined under conditions of high ( >or= 450 mmHg) and low <or= 50 mmHg) O2 tension. Similarly, decreases in pressure produced by adenosine triphosphate (ATP) and arachidonic acid (AA) were examined. The effects of these autacoids on the fetoplacental vasculature during low oxygen perfusion was compared to that obtained following nitric oxide synthase inhibition with N omega-nitro-L-arginine, (L-NOARG, 100 microns). Increases in FAP caused by ET-1, U46619, and 5-HT on fetoplacental blood vessels were not altered significantly at low oxygen tension, although that in response to BK was enhanced. Increases in FAP caused by A II were unchanged at low oxygen tension. ATP-induced decreases in FAP were reduced whereas AA-mediated changes were unchanged. Both low oxygen tension and L-NOARG produced an elevation in basal perfusion pressure. Perfusion of the human placenta with Krebs' solution of low oxygen tension may compromise placental vascular function. Impaired placental oxygenation may contribute to the development and severity of vasoconstriction in the placenta associated with pre-eclampsia/pregnancy induced hypertension.

Hypertensive and normal pregnancy: a longitudinal study of blood pressure, distensibility of dorsal hand veins and the ratio of the stable metabolites of thromboxane A2 and prostacyclin in plasma

OBJECTIVE

By combining serial measurements of the circulating concentrations of thromboxane A2 and prostacyclin with measurements of venous distensibility (taken during the pregnancies of both normal women and those with pregnancy induced hypertension or pre-eclampsia), to test the following hypotheses: 1. that changes in the venous plasma ratio of thromboxane (TXB2) and 6-keto-PGF1 alpha would correlate with changes in the blood pressure of women developing and recovering from pregnancy induced hypertension or pre-eclampsia and 2. that changes in venous distensibility would correlate with changes in arterial blood pressure in pregnancy induced hypertension or pre-eclampsia.

DESIGN

Prospective, longitudinal cohort study.

SETTING

John Hunter Hospital clinic, Newcastle, Australia.

SUBJECTS

One hundred and sixty primiparous women, recruited when presenting for their first routine antenatal visit, were investigated at, or close to, 19, 28 and 37 weeks of gestation; a subgroup was also studied in the postnatal period. The measurements of the patients who developed pregnancy induced hypertension or pre-eclampsia were compared with those of controls selected from the cohort.

MAIN OUTCOME MEASURES

Serial measurements of the circulating concentrations of the stable metabolites of thromboxane A2 and prostacyclin (TXB2 and 6-keto-PGF1 alpha, respectively), venous distensibility and immediate (no rest) and resting (for at least 30 min) blood pressures.

RESULTS

There was no significant difference between the subject and control groups at any time during or after the pregnancy in the concentrations of prostaglandin metabolites, their ratio or venous distensibility. In contrast, there was a significant difference between the groups at 19 weeks for immediate and resting readings of diastolic pressure (6 mmHg (95% CI 1.5 to 10.5) and 4 mmHg (95% CI 0.1 to 7.9), respectively). These differences increased through the pregnancy but mean postnatal readings for the groups were almost identical suggesting that the subjects were not intrinsically hypertensive compared with controls. Blood pressures for the subject group, both immediate and resting, were significantly different from the 19 week readings at 28 weeks (diastolic) and at 37 weeks (systolic and diastolic). The only significant change from first readings among controls was in postnatal systolic pressure which was significantly higher than 19 week values, probably reflecting the vasodilatation, with accompanying hypotension, of early, normal pregnancy. This difference was not observed in those who subsequently developed pregnancy induced hypertension or pre-eclampsia.

CONCLUSIONS

Our study was unable to demonstrate differences in circulating metabolites or venous distensibility between normotensive women and those with pregnancy induced hypertension or pre-eclampsia. If pregnancy induced hypertension or pre-eclampsia in humans represents not so much the presence of abnormal constrictor influences as a process initiated by failure of normal vasodilatation in early pregnancy, studies carried out later may detect mainly adaptive and secondary changes.

Vascular responses to sodium nitroprusside in the human fetal-placental circulation

This study examined the activity of sodium nitroprusside (SNP) in the human fetal-placental circulation in vitro in pathological and experimental conditions in which vascular function may be impaired. SNP (13-3400 nM) caused a concentration-dependent reduction in fetal arterial perfusion pressure (FAP) in Krebs' perfused placental cotyledons, at basal tone and following pre-constriction with prostaglandin F2 alpha (PGF2 alpha). SNP-induced reduction in FAP in the PGF2 alpha pre-constricted fetal-placental circulation was enhanced approximately six-fold (5.85) in those placentae pre-treated with the nitric oxide (NO) synthase inhibitor N omega-nitro-L-arginine (100 microM). Reductions in FAP in the preconstricted fetal-placental vasculature caused by SNP were not altered by prior infusion of ouabain (100 nM) into the fetal circulation or during low oxygen perfusion (O2 tension < 50 mmHg). No differences were observed in the responses obtained to SNP in placentae obtained from women with normotensive pregnancies or those associated with (i) pregnancy-induced hypertension, (ii) intra-uterine growth retardation, or (iii) an elevated umbilical-artery Doppler-ultrasound systolic/diastolic ratio, in either preconstricted placentae or those at basal tone. These findings are consistent with an up-regulation of guanylate cyclase/cGMP-mediated vasodilatation in the fetal-placental vasculature following complete blockade of endogenous NO production.

Autacoids and control of human placental blood flow

1. Humans have a haemochorial, villous placenta. Uterine blood passes through maternal sinuses, bathing placental villi through which fetal blood circulates. Blood flow through each circulation is high and vascular resistance low. This haemodynamic situation is essential for efficient placental function. 2. The low placental vascular resistance is due to a lack of nervous influences together with pregnancy-induced changes promoting vasodilatation. Increases occur in output of the vasodilators prostacyclin and nitric oxide and also in membrane sodium pump activity. 3. Many autacoids are present in umbilical blood. Fetal vessels of the placenta develop intense vasoconstriction in the presence of some autacoids, such as thromboxane A2 and prostaglandins F2 alpha and E2, and respond weakly to others, such as angiotensin II and 5-hydroxytryptamine. Nevertheless, vasodilator influences predominate. 4. The diseases of pre-eclampsia and fetal growth retardation are associated with reduced output of nitric oxide and prostacyclin and with increased production of thromboxane A2 and endothelin-1. These changes promote vasoconstriction, increased vascular sensitivity to vasoconstrictor stimuli, platelet aggregation and intravascular coagulation, retarding blood flow and feto-placental growth. 5. Aspirin and glyceryl trinitrate have been investigated for possible therapeutic use in pre-eclampsia and fetal growth retardation. Improved drug therapy is likely as knowledge increases of the importance of autacoids in normal placental function and in the changes that occur during disease.

Effect of inhibition of nitric oxide synthase and guanylate cyclase on hydralazine-induced vasodilatation of the human fetal placental circulation

1. The vasodilator effects of hydralazine in vitro, using the Krebs' perfused human placental lobule was studied. Single placental lobules were bilaterally perfused (maternal and fetal sides 5 mL/min each, 95% O2, 5% CO2, 37 degrees C) and changes in fetal arterial pressure (FAP) and venous outflow (VO) were recorded. 2. Submaximal vasoconstriction was induced by KCl (20-50 mmol/L), which increased basal FAP from 22.8 +/- 1.7 to 91.3 +/- 3.9 mmHg (n = 9, P < 0.001), and decreased VO from 4.1 +/- 0.6 to 0.2 +/- 0.1 mL/min (n = 6, P < 0.01). 3. Hydralazine caused vasodilatation (IC50 1.9 mmol/L, n = 9) and increased VO in the presence of KCl-induced vasoconstriction. 4. Infusion of N omega-nitro-L-arginine (100 mumol/L) to block nitric oxide synthase caused the basal FAP to increase from 30.9 +/- 5.9 to 47.4 +/- 6.7 (n = 6, P < 0.05) and significantly potentiated hydralazine-induced vasodilatation (n = 7, P < 0.05). 5. The soluble guanylate cyclase inhibitor LY 83583 (6-anilino-5,8-quinolinedione) (1 mumol/L) significantly antagonized the vasodilatation produced by hydralazine (n = 5, P < 0.05). 6. Thus, Hydralazine appears to activate guanylate cyclase, leading to increased cyclic GMP in fetal arterial vascular smooth muscle to cause vasorelaxation. No evidence was obtained to suggest that hydralazine exerted its action by either releasing nitric oxide from endothelial cells in the placenta or acting as a nitric oxide donor.

Modulation by adenosine of thromboxane A2 receptor-mediated constriction in the human umbilical artery

The powerful vasoconstrictor autacoid thromboxane A2 (TxA2) has pathological roles in many diseases including pre-eclampsia or pregnancy induced hypertension (PIH). Adenosine and other purines are released by tissues during ischemia as occurs in the utero-placental circulation during PIH. These substances, particularly adenosine, may modulate TxA2 constrictor responses. We therefore characterized TxA2 receptors in the umbilical artery in vitro using the competitive antagonist GR32191. Also examined was the Ca2+ channels' involvement in adenosine-induced inhibition of TxA2 vasoconstriction. Results showed that TxA2 receptors on umbilical arteries are identical to those present in platelets, the placenta and umbilical vein. Adenosine was found to inhibit equally constriction involving either voltage or receptor operated Ca2+ channels.

Vascular actions of purines in the foetal circulation of the human placenta

1. The vasoactive effects of adenosine triphosphate (ATP), adenosine and other purines in the foetal circulation of the human placenta were examined. Single lobules of the placenta were bilaterally perfused in vitro with Krebs buffer (maternal and foetal sides 5 ml min-1 each, 95% O2:5% CO2, 37 degrees C). Changes in foetal vascular tone were assessed by recording perfusion pressure during constant infusion of each purine. To allow recording of the vasodilator effects, submaximal vasoconstriction was induced by concomitant infusion of prostaglandin F2 alpha (0.7-2.0 mumol l-1). 2. ATP (1.0-100 mumol l-1) usually caused concentration-dependent reductions in perfusion pressure. However, biphasic with initial transient increases, or only increases in pressure were sometimes observed. Falls in pressure caused by ATP were significantly reduced by addition to the perfusate of NG-nitro-L-arginine (L-NOARG) (100 mumol l-1) but not NG-nitro-D-arginine (D-NOARG) (100 mumol l-1). They were not influenced by addition of indomethacin (10 mumol l-1) or L-arginine (100 mumol l-1). 3. Adenosine (0.01-1.0 mmol l-1) consistently caused concentration-dependent reductions in perfusion pressure, this effect not being influenced by indomethacin. L-NOARG, but not D-NOARG, reduced the potency of adenosine approximately three fold. L-Arginine, but not D-arginine enhanced its potency by a similar amount. 4. 2-Methylthio-ATP, a selective P2 gamma agonist was approximately 50 times more potent than ATP as a vasodilator agent, always causing decreases in perfusion pressure. 5. Beta-gamma-Methylene ATP, a selective P20 agonist, was approximately 100 times more potent than ATP as a vasoconstrictor, but only caused transient increases in perfusion pressure.6. The rank order of vasodilator potencies of a selection of adenosine receptor agonists was, 2-chloroadenosine>>5-(N-cyclopropyl)-carboxamidoadenosine, >5-N-ethylcarboxamidoadenosine, >2-chloro-N6-cyclopentyladenosine, >CGS-21680 > N6-cyclohexyladenosine = adenosine. Vasodilatation due to adenosine was inhibited by the PI-A2 receptor antagonist 3,7-dimethyl-l-propargylxanthine(DMPX).7. These results suggest that ATP may cause an endothelium-dependent vasodilatation in the foetal vessels of the human placenta via activation of a P2y receptor linked to the formation of nitric oxide(NO). Vasodilatation caused by ATP may mask an accompanying vasoconstrictor effect mediated, via a P2X receptor, in the villous vascular smooth muscle. Adenosine acting on P1-A2 receptors, which are also present in the foetal vasculature, may require synergistic interaction with NO to achieve a maximal vasodilator response.

Release of a substance from the human placenta having digoxin-like immunoreactivity

1. The human placental lobule, perfused with a constant flow (5 mL/min) of Krebs' solution after delivery at term, released into the fetal perfusate a digoxin-like substance, as measured by a fluorescence polarization immunoassay. 2. Initially the venous concentration was 360 +/- 66.7 pmol/L digoxin equivalents. This level did not change significantly during fetal vasoconstriction induced by prostaglandin F2 alpha infusion and persisted for the duration of the experiment (1.5-2 h). 3. Infusion into the fetal circulation of Fab fragments of sheep antibodies to digoxin caused vasodilatation, indicated by a fall in perfusion pressure. 4. Thus a digoxin-like immunoreactive substance, previously reported to be present in the placenta, is released into the fetal circulation and may play a role in placental control of fetal vascular tone.

Evidence for inhibition by endothelium-derived relaxing factor of thromboxane A2 receptor-mediated vasoconstriction in the fetal vessels of the human perfused placenta

Three inhibitors of the release or effects of endothelium-derived relaxing factor (EDRF), N-nitro-L-arginine, methylene blue and oxyhemoglobin, caused further increases in perfusion pressure during vascular constriction with submaximal concentrations of the thromboxane A2-mimetic, U46619 in fetal vessels of human placental lobules perfused in vitro. The results suggest the EDRF, released during constriction of fetal placental vessels in response to thromboxane A2 receptor stimulation, attenuates the vasoconstrictor response. Hence, impairment of EDRF release or function could contribute to the reduced placental blood flow observed in various disease states associated with increased thromboxane A2 production such as pre-eclampsia.

The effects of chronic maternal hypotension during pregnancy

The relationship between chronic maternal hypotension and obstetric outcome was examined retrospectively in a group of 134 pregnant women and compared with a normotensive control group. The hypotensive women had significantly increased risks of delivery before the 38th week of gestation, lower birth-weight of babies for gestational age, and postpartum complications. In addition, the rates of preterm delivery before 37 weeks' gestation, birth-weight less than 2,500 g and significant meconium-staining of the amniotic fluid were higher in the hypotensive group, although these results did not reach statistical significance. These data support the need for a prospective study of the effects of chronic hypotension during pregnancy.

AUTACOIDS AFFECTING VASCULAR TONE IN THE HUMAN FETAL EXTRACORPOREAL CIRCULATION

1. The human fetal extracorporeal circulation is normally a vasodilated, low pressure system. 2. As this vasculature lacks innervation, autacoids have been postulated as being of great importance in controlling its tone. 3. This has now been confirmed by pharmacological in vitro techniques, particularly utilizing perfusion of the isolated umbilical cord and placental lobule. 4. The fetal umbilical-placental vessels are sensitive to a wide range of vasoconstrictor autacoids, some of which can cause intense vasospasm. 5. Thromboxane A2 receptors have been identified in both umbilical vein and placental villous vessels. 6. Prostacyclin and endothelial cell-derived relaxing factor (or nitric oxide) may be largely responsible for the low vascular resistance normally found in the fetal extracorporeal circulation. 7. Immediately after birth it is likely that stimuli such as cooling, stretching and handling of the umbilical cord cause release of eicosanoids and other autacoids from the vessels, leading to their complete closure.

Self-reported long-term outcomes of hysterectomy

OBJECTIVES

To investigate women's perceptions of and satisfaction with the long-term outcomes from a hysterectomy performed between 2 and 10 years ago and to determine whether satisfaction is related to demographic factors, factors associated with the hysterectomy, and the number or type of perceived benefits and problems associated with the hysterectomy.

DESIGN

Retrospective survey by telephone interview and postal questionnaire of 236 women who had a hysterectomy between 2 and 10 years ago.

SETTING

Women who had had a hysterectomy were identified from a community survey in the Hunter Region of NSW, Australia.

SUBJECTS

Two hundred and thirty-six women who self-reported having had a hysterectomy between 2 and 10 years ago.

MAIN OUTCOME MEASURES

Perceived benefits resulting from the hysterectomy; perceived physical and psychological problems caused by the hysterectomy; satisfaction with care.

RESULTS

Relief from heavy bleeding was the most frequent benefit (57%) and the most important benefit (32%). Most of the women reported improvements in symptoms experienced before hysterectomy but more than half the women had symptoms which they believed had been worsened or caused by the hysterectomy. Despite this, high levels of satisfaction with the operation were reported.

CONCLUSION

The results highlight the need to examine more closely decision-making about treatment for menstrual symptoms such as heavy bleeding.

Regulation of fetal vascular tone in the human placenta

Using an in vitro placental lobule perfusion technique, the human fetal placental vasculature has been found to respond vigorously with high sensitivity to various vasoconstrictor substances, including angiotensin II, endothelins 1 and 3, prostaglandins F2 alpha, E2 and D2 and the thromboxane A2 agonist U46619. Thromboxane A2 receptors mediating vasoconstriction have been characterized in fetal placental vessels and appear to be identical to those on human platelets and pulmonary blood vessels. Although the isolated fetal placental vessels are largely unresponsive to exogenous vasodilatory stimuli, when preconstricted they respond by vasodilatation to several vasodilator substances, including arachidonate, prostacyclin, prostaglandin E1, theophylline and nitroglycerine. The resistance offered to flow in vitro by the villous vasculature is therefore low, as it is in vivo. Both intrinsic and extrinsic mechanisms probably operate to cause relaxation of the vascular smooth muscle with the vasodilatory effects of locally released autacoids dominating the effects of those having vasoconstrictor actions.

Ethical aspects of surrogacy

Ethical issues related to surrogacy are explored and an argument made for its ethical approval in circumstances where the particularities of the case warrant this approach to reproduction. Despite recent and impending legislation to prohibit commercial surrogacy in some States of Australia, although data are difficult to obtain, unofficial and anecdotal reports from medical practitioners specializing in the management of infertility throughout the country indicate an increasing number of requests for surrogacy and increasing referral of infertile couples to the USA for commercial surrogacy arrangements.

Changes in the biological activity of autacoids during passage through the human perfused fetoplacental lobule

Changes in the biological activities of a number of autacoids after a single passage through the human perfused fetoplacental lobule have been assessed by bioassay, whilst recording fetal vascular resistance. Bradykinin did not affect vascular resistance, but its biological activity on the superfused bioassay tissues fell by approximately 98%, whereas des-Asp1-angiotensin I activity increased at least 80-fold and the vascular resistance rose. All these effects were inhibited by captopril. Angiotensin II increased vascular resistance but its activity on the bioassay tissues was not changed. 5-Hydroxytryptamine activity was reduced by 67-90% and resistance to flow was not affected. The activities of prostaglandins D2, E2, and F2 alpha were slightly reduced. Prostaglandins D2 and F2 alpha caused vasoconstriction, their maximum effects being greater than those of either of the angiotensins. The TxA2-mimetic U46619 was approximately 90 times more potent than PGF2 alpha, as a vasoconstrictor, but the maximal effects were comparable. Thus, autacoid activity can be reduced, augmented or not affected during passage through the human perfused fetal placental vasculature.

Ovarian stromal and luteal tissue prostaglandins, 17 beta-estradiol, and progesterone in relation to the phases of the menstrual cycle in women

The concentrations of prostaglandin F2 alpha, prostaglandin E2, the 15-keto-13, 14-dihydro-metabolite of prostaglandin F2 alpha, progesterone, and 17 beta-estradiol were measured in 31 ovarian stromal tissue and 18 luteal tissues. Tissue samples were obtained during abdominal hysterectomy. The ovarian stromal tissue prostaglandin F2 alpha content during the late secretory and early proliferative phases was significantly higher (p less than 0.001) than in tissues obtained during any other phases of the menstrual cycle. The ovarian stromal tissue prostaglandin E2 content was significantly elevated (p less than 0.01) during the late proliferative and early secretory phases. The content of the prostaglandin F2 alpha metabolite also was elevated (p less than 0.001) in ovarian stromal tissues obtained during the late proliferative and early secretory phases. Comparison of the concentrations of prostaglandins and sex steroids in ovarian stromal and luteal tissues indicate the latter to be far more active in terms of steroid and arachidonate metabolism. During the early luteal phase, when the luteal progesterone content was at its highest, both luteal and ovarian stromal tissue contents of prostaglandin E2 were also elevated. The late secretory phase of the menstrual cycle was characterized by lowered luteal progesterone content and a markedly elevated level of prostaglandin F2 alpha in luteal and ovarian stromal tissues. During cyclic ovarian activity in the woman, prostaglandin E2 predominated during the periovulatory phases while the period of luteal death was highlighted by the elevated prostaglandin F2 alpha content in ovarian stromal and luteal tissues.

Attenuation of pressor responses to sympathetic stimuli in the rat by enalapril

Intravenous administration to pithed Wistar rats of the angiotensin converting enzyme inhibitor enalapril (0.1-1.0 mg/kg) lowered the diastolic blood pressure and reduced pressor responses occurring during electrical stimulation (1-30 Hz) of the spinal sympathetic outflow. These doses of enalapril given intravenously also attenuated pressor responses to intravenous injection of the muscarinic ganglion stimulant McNeil-A-343 (50, 100, 150 micrograms/kg) and noradrenaline (0.1-5.0 micrograms/kg). Enalapril (1.0 mg/kg, i.v.) reduced pressor responses to the nicotinic ganglion stimulant 1,1-dimethyl-4-phenyl-piperazinium (300 micrograms/kg, i.v.). These results confirmed that the actions of enalapril resemble those of captopril in the pithed rat, by causing reductions in both blood pressure and pressor responses to sympathetic stimuli.

Acetylcholine output and foetal vascular resistance of human perfused placental cotyleda

The foetal villous vessels of single cotyleda of human placentae have been perfused with a constant flow of Krebs solution, recording inflow pressure and passing the venous perfusate in cascade over guinea-pig ileum and rat stomach strip preparations in vitro. Each cotyledon released for at least 4 h a substance that was probably acetylcholine. The perfusate caused contractions of both preparations which were inhibited by atropine or hyoscine and potentiated by physostigmine. Contractile activity was destroyed after incubation at 37 degrees C of perfusate with acetylcholinesterase but not with acetylcholinesterase plus physostigmine. When the perfusion temperature was lowered to 34 degrees C or below, acetylcholine output was reduced, the extent depending on the fall in temperature. No change in resistance of the villous vessels occurred during the changes in temperature or in the presence at 37 degrees C of atropine, hyoscine, hexamethonium, (+)-tubocurarine, hemicholinium-3 or bretylium. Submaximal vasoconstrictor responses of the villous vessels to the thromboxane A2-mimetic U46619 were not affected by reduction of the perfusion temperature to 30 degrees C, which lowered acetylcholine-like output by approximately 70%. Responses to U46619, at 37 degrees C, were unchanged during the presence of atropine or hyoscine. Acetylcholine is released into the foetal circulation of the human placenta but no evidence could be obtained that it affects villous vascular smooth muscle tone or vasoconstrictor responses.

Haemodynamic changes and left ventricular performance during high-dose oestrogen administration to male transsexuals

Serial haemodynamic and systolic time interval measurements in 17 male transsexuals during high-dose oestrogen administration were compared with control values obtained after oestrogen withdrawal. During oestrogen treatment, cardiac output, stroke volume, plasma volume and total blood volume increased while total peripheral resistance, diastolic blood pressure and red cell mass decreased significantly. Changes in heart rate and systolic blood pressure were not significant. Despite a much higher dose of oestrogen, the haemodynamic changes observed in this study are similar in magnitude to those occurring in women taking oral contraceptives. Significant changes in systolic time intervals during oestrogen treatment were a shortened pre-ejection period (PEP) index, a prolonged left ventricular ejection time (LVET) index and a decreased PEP/LVET ratio indicating that left ventricular performance was augmented.

Characterization of thromboxane A2 receptors in the human fetal placental vessels and umbilical vein

An in vitro examination has been made of the thromboxane A2 receptors in human fetal placental villous vessels and umbilical veins utilizing the TxA2 agonist U46619 and its competitive antagonist AH22921. U46619 was a potent constrictor of both preparations. The EC50 were 25.3 nmol/l (s.e.m. = 2.5, n = 8) for causing constriction of perfused villous vessels and 22 nmol/l (s.e.m. = 5, n = 17) for contraction of the venous longitudinal strip. AH22921 competitively antagonized responses to U46619 in both preparations. The pA2 values were not significantly different and their 95% confidence limits, obtained for its ability to antagonize responses to U46619 in villous vessels and the umbilical vein, were 8.0 (7.3-8.8) and 7.1 (6.3-7.9) respectively. It is concluded that TxA2 receptors in both the human fetal placental villous vessels and umbilical vein may be similar. They also may be similar to those in human platelets and pulmonary blood vessels.

Changes in lymphocyte status and responsiveness in pregnancy detected by a fluorescent cell probe

Lymphocyte reactivity assessed by a fluorescent lipophilic probe test of responsiveness to concanavalin A (con A) was shown to differ from normal in early pregnancy. The difference was most marked in multiparas. Abnormal reactivity was detected in the earliest pregnancy examined (5 weeks' gestation) and up to about the 20th week; after 20 weeks, reactivity was normal in all of the multiparas and most of the nulliparas studied. However, in pregnancy induced hypertension (PIH), a disorder of late pregnancy, the same responsiveness as in early pregnancy was found. When unstimulated lymphocytes were examined, abnormal reactivity associated with increased fluorescence was observed in early pregnancy and in PIH, compared with normal late pregnancy, reflecting alteration in lymphocyte membrane phospholipids. It is postulated that pregnancy is associated with sequential change in immunity, disturbance of which may result in immunologically-determined obstetric morbidity.

Lymphocyte subclasses in pregnancy induced hypertension

Peripheral blood lymphocyte subclasses were studied by flow cytofluorimetry and monoclonal antibodies in 21 women with Pregnancy Induced Hypertension (PIH), 20 healthy women in their third trimester of pregnancy and in 20 nulliparous, nonpregnant women. The cells were stained with the monoclonal antibodies OKT3, OKT4 and OKT8 to define total T cells, T helper cells (Th) and T suppressor-cytotoxic cells (Ts/c) respectively. B lymphocytes were defined by their surface immunoglobulin. Absolute numbers of total T cells and Ts/c cells were significantly decreased (p less than 0.05) in patients with PIH compared to either control group. The proportion of B lymphocytes was significantly (p less than 0.01) increased and absolute numbers were marginally increased. These findings reflect an immune disturbance which may be of prime importance in the pathogenesis of this disease.

Antenatal intrauterine diagnosis of fetal thalassaemia

The results are reported of the intrauterine diagnosis of fetal thalassaemia in 72 pregnant women investigated during the six years from 1977 to 1982. In the majority of cases fetal blood was collected by fetoscopy for globin chain synthesis at 18 to 19 weeks' gestation. Adequate fetal blood samples for the diagnosis of the thalassaemia status of the fetus were obtained in 85% of cases. The technical difficulties associated with fetoscopy and fetal blood collection are discussed, and the maternal and fetal complications of the procedure described.

Effects of vasoactive autacoids on the human umbilical-fetal placental vasculature

Studies have been made of the effects of autacoids on vascular tone of the human perfused fetal umbilical vein and placental lobule. The thromboxane A2 (TxA2)-mimetic substance U46619, 5-hydroxytryptamine and bradykinin were powerful constrictors of the vein. Prostaglandins E2 (PGE2), F2 alpha (PGF2 alpha), adrenaline, noradrenaline, histamine and angiotensin II were much less potent. Venoconstriction caused by U46619, bradykinin and 5-hydroxytryptamine was reduced during inhibition of phospholipase A2 with mepacrine. Responses to U46619 were also reduced after inhibition of cyclo-oxygenase with indomethacin whereas those to bradykinin and 5-hydroxytryptamine were potentiated. In the placenta U46619 was the most potent vasoconstrictor, bradykinin, 5-hydroxytryptamine, angiotensin II, PGE2 and PGF2 alpha being 10-100 times less active. Responses to U46619 were reduced by either mepacrine or indomethacin. Arachidonic acid caused umbilical venoconstriction but vasodilatation in the placenta. Both effects were reduced by indomethacin. Prostacyclin (PGI2) caused vasodilatation in both preparations. It is suggested that TxA2 in the placenta and TxA2, 5-hydroxytryptamine and bradykinin in the umbilical vein could contribute to control of vascular smooth muscle tone. Their vasoconstrictor effects are partly indirect and affected by the concomitant local release of eicosanoids. The results add support to previous conclusions that these autacoids may normally have important influences on blood flow in the fetal extra-corporeal circulation. Agents inhibiting their synthesis, eg non-steroidal anti-inflammatory agents, should only be prescribed during pregnancy with these facts in mind.