Fetoplacental vascular responses to prostacyclin after thromboxane-induced vasoconstriction

The vasodilator prostacyclin is produced by fetal tissues and may serve to protect umbilical blood flow. We hypothesized that prostacyclin could reverse fetoplacental vasoconstriction produced by a thromboxane mimic (U-46619). Fetal regional blood flow was measured by the radioactive microsphere technique in six unanesthetized, near-term ovine fetuses. Measurements were made in the control period, again 20 minutes after a fetal infusion of U-46619 was begun, and finally 20 minutes after prostacyclin was added to the U-46619 infusion. Mean arterial pressure rose significantly in response to U-46619 (38 +/- 1 to 51 +/- 2 mm Hg, p less than 0.01) and returned to baseline after prostacyclin (42 +/- 2 mm Hg). Renal resistance was increased from 0.16 +/- 0.01 to 0.22 +/- 0.01 mm Hg.ml-1.min.100 gm-1 (p less than 0.05) by U-46619 and decreased significantly (p less than 0.05) below baseline by addition of prostacyclin (0.10 +/- 0.02 mm Hg.ml-1.min.100 gm-1). Placental resistance also increased significantly (p less than 0.03) in response to U-46619 (from 0.15 +/- 0.01 to 0.21 +/- 0.01 mm Hg.ml-1.min.kg-1 fetal weight) but was further increased to 0.29 +/- 0.03 mm Hg.ml-1.min.kg-1 fetal weight by the addition of prostacyclin. Umbilical placental blood flow decreased significantly (p less than 0.03) when prostacyclin was added to U-46619 (315 +/- 40 to 195 +/- 30 ml.min-1.kg-1 fetal weight). Whereas U-46619 had no effect on fetal arterial blood gases, the addition of prostacyclin resulted in significant fetal acidosis (p less than 0.03). We conclude that thromboxane mimic causes fetal hypertension and renal and placental vasoconstriction. Prostacyclin reverses hypertension and renal vasoconstriction but, unexpectedly, worsens fetal placental vasoconstriction produced by thromboxane. It is likely that the observed fetal acidosis is a result of compromised placental function.     

Vasodilatory response of fetoplacental vasculature to adrenomedullin after constriction with the thromboxane sympathomimetic U46619

OBJECTIVE: This study was undertaken to determine whether adrenomedullin, a hypotensive peptide, decreases vasomotor tone in fetoplacental vasculature that has been constricted with the thromboxane sympathomimetic U46619. STUDY DESIGN: The fetoplacental vascular beds of 20 perfused human placental cotyledons were vasoconstricted with a continuous infusion of U46619 (10(-8) mol/L). The vasculature was then sequentially injected with deionized water, 30 ng adrenomedullin, 300 ng adrenomedullin, and 3000 ng adrenomedullin. Any change in perfusion pressure was noted after each dose. In a separate experiment the fetoplacental vasculature in 2 perfused cotyledons from each of 10 placentas was vasoconstricted with U46619 (10(-8) mol/L). Adrenomedullin was infused continuously at either 200 ng/min (n = 5) or 2000 ng/min (n = 5) for 40 minutes. A corresponding control cotyledon from each placenta had isotonic sodium chloride solution added to its perfusion. Perfusion pressures were recorded every minute during the infusion and for 40 minutes afterward. Analysis of variance was used to compare pressure changes in the cotyledons that received bolus doses of adrenomedullin. Paired t tests of mean percentage pressure changes were used to compare the study and control groups that received the continuous infusions. RESULTS: In the cotyledons that received bolus doses of adrenomedullin, the mean (+/-SEM) percentage perfusion pressure changes from the baseline were -6.7 +/- 0.5 for 30 ng adrenomedullin (P =.0039), -8.5+/- 0.7 for 300 ng adrenomedullin (P <.0001), and -13.1 +/- 1.0 for 3000 ng adrenomedullin (P <.0001). With the continuous adrenomedullin infusion of 200 ng/min, there was no significant difference in the mean percentage pressure change from baseline between the study and control groups (-0.57%). At 2000 ng/min there was a significant difference (-15.34%; P <.0001). CONCLUSION: Adrenomedullin caused vasodilatation of fetoplacental vasculature previously constricted with the thromboxane sympathomimetic U46619 in the isolated perfused placental cotyledon. This vasodilatation occurred in a dose-dependent manner.     

Fetal infusions of plasma cause an increase in umbilical vascular resistance in sheep

Earlier studies suggested that the fetal placental circulation is relatively inert with fetal placental flow increasing or decreasing with perfusion pressure. Subsequent studies have demonstrated that the placenta may not be an unreactive vascular bed. The present study was undertaken to determine if plasma infusion-induced hypertension increased fetal placental flow in proportion to the driving pressure across the fetal placental circulation. Six fetal sheep were operated on at 118-122 days to place intravascular catheters and a flow sensor on the common umbilical artery. Starting 6 days later, the fetuses were infused with adult sheep plasma. During the 7-day-long infusion period, they received a total of 1515+/-217 (SD) ml of fluid and 93.2+/-12.0 g of protein. Fetal plasma protein concentrations increased from 34.2+/-2.3 to 77.0+/-9.7 g/l (P<0.0001). Fetal arterial blood pressures rose from 42+/-3 to 59+/-4 mmHg (P<0.01) and venous pressures rose from 2.2+/-0.5 to 4.8+/-0.8 mmHg (P<0.01). In spite of the large increase in driving pressure, fetal placental blood flow remained (statistically) constant (627+/-299 ml/min and 552+/-221 ml/min) while fetal umbilical resistance increased from 0.077+/-0.038 to 0.115+/-0.053 mmHg min/ml (P<0.01). On day 7, plasma renin activity had fallen from 6.7+/-4.2 ng/(ml/h) at preinfusion control to 0.6+/-0.6 ng/(ml/h) (P<0.05) and plasma angiotensin-II concentration had fallen from 33.2+/-26.6 to 6.2+/-3.9 pg/ml, although this fall was not statistically significant (P=0.07). Fetal placental flow did not increase with increased driving pressure across the fetal placental circulation. The increase in fetal placental resistance may be a response to the increase in arterial pressure since there was no increase in flow.     

Vasoactive responses of veins isolated from the human placental chorionic plate

The control of the blood flow within the fetoplacental circulation is poorly understood despite the essential role of the placenta in pregnancy. Our aim was to assess the vasoactive responses of veins from the placental chorionic plate.Biopsies were obtained from term placentae from uncomplicated pregnancies. Small veins from the chorionic plate were dissected free from surrounding tissue and studied using parallel wire myography.Human placental chorionic plate veins developed maintained constrictions to the thromboxane-mimetic U46619. Endothelium-dependent agonists did not promote venous relaxation. However, NO donation with the endothelial-independent agent, sodium nitroprusside, elicited significant relaxation. Venous constriction to U46619 and relaxation to sodium nitroprusside were modified by adjustment of media oxygen tension and normalization parameters.Human placental chorionic plate veins respond to vasoactive agents and may play a role in the control of the blood flow in the fetoplacental circulation.     

Vasoactivity to and endogenous release of vascular endothelial growth factor in the in vitro perfused human placental lobule from pregnancies complicated by preeclampsia

Vascular endothelial growth factor (VEGF) is a potent, physiologically relevant, vasodilator of the human term fetoplacental vasculature of placental lobules from normal pregnancy. There is evidence that VEGF and its receptors are dysregulated in preeclampsia (PE). Here, we used dual perfusion of the human placental lobule to test the hypothesis that the VEGF vasodilatory effect on the fetoplacental circulation is altered in PE and examined how vascular responsiveness relates to circulating levels of free VEGF in fetal sera in this disease. Umbilical cord sera and fetal venous perfusate concentrations of free VEGF from pregnancies complicated with PE were significantly lower compared to the normal group (P<0.05 and P<0.01, respectively). There was elevated in vitro placental release of the sequestrating soluble receptor, sVEGFR-1, into the fetal-side perfusate with PE compared to the normal group (P<0.05). The umbilical sera PlGF-1 level was higher by an order of magnitude in the fetal circulation in PE compared to normal pregnancy (P<0.0001), with the placenta appearing to contribute appreciably to these levels. Placental net contribution to maternal systemic free VEGF levels appeared to be negligible in both groups. sVEGFR-1 levels were elevated in the maternal-side venous perfusate with PE compared to the normal pregnancy (P<0.01). Perfused lobules from PE pregnancy exhibited an enhanced fetoplacental vasodilatory response to exogenous VEGF (P<0.001), with a longer recovery time (P<0.05), compared to the normal control group. Extrapolation of our combined functional and biochemical data suggests that a decrease in the in vivo circulating levels of free VEGF in PE is likely to contribute to compromised fetoplacental vascular patency in this disease.     

Reactivity of human placental chorionic plate vessels is modified by level of oxygenation: differences between arteries and veins

Normal fetal development in utero is dependent upon adequate perfusion of the placental vasculature, yet how fetoplacental blood flow is matched to maternal blood flow is unknown. In the perfused placental cotyledon in vitro, reduced oxygenation promotes vasoconstriction, which may act to direct blood in fetoplacental vessels to effectively perfused regions of the intervillus space. We aimed to demonstrate that oxygen tension could directly modify placental chorionic plate vessel vasoreactivity. Small arteries and veins from the chorionic plate were dissected from biopsies from term placentae of uncomplicated pregnancies and studied using parallel wire myography. Chorionic artery and vein vasoconstriction in 20%, 7% and 2% oxygen was assessed utilizing the thromboxane-mimetic U46619. Reduced oxygenation increased arterial maximal active effective pressure production and sensitivity to U46619. This effect was cyclo-oxygenase independent. In veins, modified oxygenation did not alter vasoconstriction. Vasodilatation in response to the NO donor sodium nitroprusside was increased in lowered oxygenation in veins but not in arteries. We suggest that modified oxygenation may play a role in the control of the blood flow in the fetoplacental circulation.     

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.     

Vasoconstriction of small arteries isolated from the human placental chorionic plate in normal and compromised pregnancy.

Our aim was to compare placental chorionic plate small artery function in normal pregnancies and those complicated by preeclampsia and intrauterine growth restriction. In particular we wished to test the hypothesis that the constrictive potential of placental small arteries is modified in compromised pregnancy. Biopsies were obtained from term placentas from uncomplicated pregnancies and those affected by preeclampsia and intrauterine growth restriction. Small arteries from the chorionic plate were dissected free from surrounding tissue and studied using parallel wire myography. Placental small arteries developed maintained constrictions to arginine vasopressin and the thromboxane-mimetic U46619. Arterial maximal constriction was reduced in both preeclampsia and intrauterine growth restriction. This effect was agonist independent. In intrauterine growth restriction, placental small arteries showed decreased sensitivity to U46619 but not to arginine vasopressin. Human placental chorionic plate small artery vasoconstriction is significantly reduced in compromised pregnancy, a factor that may lead to altered blood flow within the fetoplacental circulation in these conditions.     

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.     

Characterisation of tone oscillations in placental and myometrial arteries from normal pregnancies and those complicated by pre-eclampsia and growth restriction

Agonist-induced tone oscillations (rhythmic contractions and relaxations) occur in vascular beds to allow acute regulation of volume flow and thus the delivery of oxygen and nutrients to the tissue. Mechanisms responsible for the control of human placental vasomotor tone and blood flow are poorly characterized. This study aimed to characterise thromboxane-induced tone oscillations in human placental and myometrial arteries. Chorionic plate and myometrial arteries obtained from biopsies at term were mounted for isometric tension measurement. Tone oscillations were observed in chorionic arteries only when exposed to sub-maximal (<1 microM) concentrations of U46619. Slow (mean+/-SEM) frequency (2.6+/-0.5 per hour), large amplitude (39+/-7% of peak contraction) tone oscillations were elicited by 0.03 microM U46619 (n=18). In the presence of the nitric oxide synthase (NOS) inhibitor l-NNA (100 microM) the amplitude was significantly reduced (40+/-13% to 18+/-8%, P<0.05, n=6), frequency was unaltered and the bradykinin-dependent vasodilator response was reduced (68+/-13% to 40+/-19%, P<0.05, n=6). Myometrial arteries exposed to 1 microM U46619 developed tone oscillations within 10 min, which increased in amplitude over 30min occurring at relatively constant frequency. The mean amplitude of oscillations at 30 min (31+/-7%, n=16) was similar to that in chorionic arteries but the occurrence more frequent (42.8+/-9.7 per hour, P<0.001). Inhibition of NOS did not alter tone oscillations in myometrial arteries. Tone oscillations in chorionic arteries from pre-eclamptic and growth restricted (FGR) pregnancies were reduced in amplitude whereas those in myometrial arteries had increased frequency. Inhibition of NOS further reduced oscillation amplitude in chorionic arteries from FGR pregnancies. The alterations may contribute to the vasculopathology of these conditions, or, may represent compensatory mechanisms to maintain a matching of materno-placental blood flow.     

Influence of magnesium sulphate and isradipine on human placental cotyledon fetal vessels in vitro.

Increased systemic vascular resistance and blood pressure during pregnancy may be due to impaired prostacycline PGI(2)-thromboxan (TX) A(2) balance. The aim of the study was to compare the influence of magnesium sulphate and isradipine on the placental vascular resistance induced by stable thromboxan A(2) analogue U 46619 in experimental bilateral perfusion of the human placental cotyledon. The research used the experimental model described by Schneider et al. [Am. J. Obstet. Gynecol. 114 (1972) 822]. The control group consisted of six placental lobule perfusions lasting 120 min each. Constant increase in perfusion pressure of mean value 185% of the initial pressure was obtained from about the 60th min of the experiment and maintained till the end. Having obtained constant increase in perfusion pressure from the 60th min of the experiment, magnesium sulphate and isradipine were administered along with thromboxan A(2) analogue U 46619 into the fetal circulation. Both drugs lowered perfusion pressure, experimentally increased by thromboxan A(2) analogue U 46619. The onset of magnesium sulphate activity was quicker than isradipine. According to the results of our in vitro study, magnesium sulphate and isradipine may have a beneficial effect on vascular resistance of cotyledon vessels in PIH in vivo, too.     

The actions of prostaglandins and their interactions with angiotensin II in the isolated perfused human placental cotyledon

The prostaglandins PGE1, PGE2, PGD2, PGF2 alpha, U46619 and 6 beta-PGI1 were administered as bolus injections both separately and in combination with angiotensin II into the fetal circulation of isolated human placental cotyledons perfused in vitro. PGF2 alpha and PGD2 caused small dose-dependent increases in fetal perfusion pressure when compared with U46619 which acted as an extremely potent vasoconstrictor of the fetal-placental vasculature. PGE1 caused very small dose-dependent decreases in fetal perfusion pressure when injected on its own. In combination with angiotensin II, PGE1, PGD2 and 6 beta-PGI1 caused significant, dose-related attenuations of the angiotensin II vasoconstrictive response whereas PGE2, PGF2 alpha and U46619 potentiated the response. Injections of angiotensin II after the infusion of indomethacin into the fetal circulation resulted in a potentiation of angiotensin II induced vasoconstriction. The results indicate that prostaglandins exert their effects on the fetal-placental circulation by modulating the actions of angiotensin II.     

Umbilical artery Doppler waveform indices from normal pregnant women are related to vasodilatation of placental chorionic plate small arteries.

Blood flow control within the fetoplacental circulation is poorly understood despite the essential role of the placenta in pregnancy. Our study compared an in vitro assessment of placental chorionic plate small artery function with in vivo measures of umbilical artery blood flow. Umbilical artery Doppler waveform analysis was performed on women (N=8) with uncomplicated pregnancies within 24 hours of delivery. Small arteries (n=25) were dissected from the placental chorionic plate from biopsies at term and studied using parallel wire myography. Chorionic plate arteries developed maintained constrictions to the thromboxane-mimetic U46619. Nitric oxide (NO) donation with the endothelial-independent agent sodium nitroprusside elicited significant relaxation compared to paired control vessels. This vasodilatation correlated significantly with both pulsatility and resistance indices measured in the umbilical artery. We conclude that Doppler indices in the umbilical artery are inversely proportional to the maximal relaxation achieved by chorionic plate small arteries in response to a NO donor.     

Oxygen tension and normalisation pressure modulate nifedipine-sensitive relaxation of human placental chorionic plate arteries

Fetoplacental blood vessel constriction in response to reduced oxygenation has been demonstrated in placenta perfused in vitro. In pulmonary vessels, hypoxic vasoconstriction involves Ca2+ influx into smooth muscle through membrane ion channels including voltage-gated Ca2+ channels (VGCCs). We hypothesised that VGCCs are involved in agonist-induced constriction of fetoplacental resistance vessels and that their contribution is modulated by oxygen. Chorionic plate small arteries were studied using wire myography. Arteries were normalised at high (0.9 of L(13.3 kPa)) or low (0.9 of L(5.1 kPa)) stretch and experiments performed at 156, 38 or 15 mmHg oxygen. At low stretch, U46619 (thromboxane-mimetic) or KCl (smooth muscle depolarisation) constriction was greater at 38 than 156 or 15 mmHg oxygen. An L-type VGCC blocker nifedipine, inhibited KCl constriction by >85% but was less effective in U46619 constrictions (43-67%). At high stretch, nifedipine inhibition of KCl- and U46619-induced constriction was less at 15 than 38 or 156 mmHg oxygen. Oxygen did not affect constriction to U46619 or nifedipine-induced relaxation when vessels were normalised at high stretch. In conclusion, oxygen modulates chorionic plate arterial constriction at low stretch but regulation is lost at high stretch. U46619 constriction is underlain by VGCCs and nifedipine-insensitive processes; their relative contribution is influenced by oxygen.     

Fetal vascular responses to prostacyclin

Prostacyclin is a potent vasodilator produced by both maternal and fetal tissues that dilates the umbilical placental vasculature in vitro. To test the hypothesis that prostacyclin dilates the fetal placental circulation in vivo, we measured blood flow by the radioactive microsphere technique in six unanesthetized near-term ovine fetuses before and during prostacyclin infusion. Fetal mean arterial pressure fell 15% from 35 +/- 3 to 31 +/- 3 mm Hg (p less than 0.05) during prostacyclin infusion, and heart rate increased from 182 +/- 6 to 208 +/- 19 beats/min (p less than 0.05). Placental blood flow changed from 240 +/- 58 to 191 +/- 46 ml.min-1.kg-1 fetal weight (p = 0.07), whereas vascular resistance was unchanged (0.16 +/- 0.04 to 0.18 +/- 0.06 mm Hg.ml-1.min.kg fetal weight). Fetal arterial pH decreased from 7.33 +/- 0.03 to 7.28 +/- 0.02 (p less than 0.05) during prostacyclin infusion, with a significant decrease in base excess from -1.2 +/- 1.4 to -3.1 +/- 1.6 (p less than 0.05) and a trend toward hypercarbia (p = 0.07). We conclude that in vivo administration of prostacyclin to the ovine fetus does not cause fetal placental vasodilation and does cause a significant fetal acidemia. The mechanism for these unexpected observations is likely shunting of blood away from the placenta to other organs in the face of systemic vasodilation.     

Characterization of small arteries isolated from the human placental chorionic plate

Despite the essential role of the placenta in pregnancy, the control of the blood flow within the fetoplacental circulation is poorly understood. A handful of myography studies have directly assessed the role of vasoactive agonists in fetoplacental vasculature contractility but have used a range of steady-state conditions. Our aim, therefore, was to determine the optimal vessel diameter and oxygen tension to assess vascular function in small arteries isolated from the chorionic plate of normal term placentae.Biopsies were obtained from term placentae from uncomplicated pregnancies. Small arteries were dissected from the chorionic plate, mounted onto a wire myograph in HCO3(-) -buffered physiological salt solution at 37 degrees C and equilibrated for 20 min.Two methods for normalization of the optimal length/diameter for contractility of chorionic plate small arteries were assessed. Both classical normalization (CN) and length-tension curve (LTC) methods produced similar data. These data were agonist-independent.Data for CN and LTC were unaffected but maximal force generation (for U46619) was decreased in reduced oxygen tensions.Using conditions for optimal tension production in chorionic plate small arteries the thromboxane-mimetic U46619 produced the greatest and most reproducible constrictive effect. Relaxations were only achieved with endothelial-independent agonists (sodium nitroprusside and papaverine).     

Fetomaternal transfusion and pregnancy outcome after cordocentesis

OBJECTIVE: To study the extent of fetomaternal transfusion and the outcome of pregnancy after cordocentesis. MATERIAL AND METHODS: 268 women underwent percutaneous fetal umbilical cord blood sampling for fetal karyotyping between 15 and 26 gestations of weeks. Complete follow-up was available in 221 (82.5%) of the cases. Cordocentesis was performed under continuous real-time ultrasound guidance. The duration of the procedure and the post-procedural bleeding time was counted in seconds. Fetomaternal transfusion was calculated by using the measurements of the maternal serum levels of alpha-fetoprotein before and after the procedure. The data were analyzed by Student's t and multiple regression tests. RESULTS: The maximum and mean amounts of fetomaternal transfusion were 1.067 and 0.061 ml, respectively. Twenty percent or more alpha-fetoprotein elevation was in 35.4% of the cases. Positive correlation was found between bleeding time after cordocentesis and fetomaternal transfusion (r = 0.174, p < 0.0129) as well as between the duration of the procedure (r = 0.165, p < 0.0171) and the amount of fetomaternal transfusion. Comparing the cordocentesis at the placental insertion site and at the free cord loop, a smaller amount of fetomaternal transfusion was observed (p < 0.0123) in the latter. Transplacental passage was associated with a higher amount of fetomaternal transfusion (p < 0.0067). No association was found between the extent of fetomaternal transfusion and the outcome of pregnancy. The fetal loss related to the cordocentesis was 0.50%. CONCLUSIONS: The extent of fetomaternal transfusion was influenced by the subsequent four parameters: procedural time, bleeding time, puncture site and transplacental penetration. The lack of the association between the degree of fetomaternal transfusion and the outcome of pregnancy, along with the low (0.50%) post-procedural fetal loss rate, suggest that cordocentesis is clinically a safe procedure.     

The actions of prostaglandins and their interactions with angiotensin II in the isolated perfused human placental cotyledon

Summary. The prostaglandins PGE₁, PGE ₂, PGD ₂, PGF _2α., U46619 and 6_β-PGI_l were administered as bolus injections both separately and in combination with angiotensin II into the fetal circulation of isolated human placental cotyledons perfused in vitro . PGF_2α, and PGD₂, caused small dosedependent increases in fetal perfusion pressure when compared with U46619 which acted as an extremely potent vasoconstrictor of the fetal-placental vasculature. PGE₁, caused very small dose-dependent decreases in fetal perfusion pressure when injected on its own. In combination with angiotensin 11, PGE₁, PGD₂, and 6_β-PG1₁, caused significant, dose-related attenuations of the angiotensin II vasoconstrictive response whereas PGE₂, PGF_2α, and U46619 potentiated the response. Injections of angiotensin II after the infusion of indomethacin into the fetal circulation resulted in a potentiation of angiotensin II induced vasoconstriction. The results indicate that prostaglandins exert their effects on the fetal-placental circulation by modulating the actions of angiotensin II.     

The actions of prostaglandins and their interactions with angiotensin II in the isolated perfused human placental cotyledon

Summary. The prostaglandins PGE₁, PGE ₂, PGD ₂, PGF _2α., U46619 and 6_β-PGI_l were administered as bolus injections both separately and in combination with angiotensin II into the fetal circulation of isolated human placental cotyledons perfused in vitro . PGF_2α, and PGD₂, caused small dosedependent increases in fetal perfusion pressure when compared with U46619 which acted as an extremely potent vasoconstrictor of the fetal-placental vasculature. PGE₁, caused very small dose-dependent decreases in fetal perfusion pressure when injected on its own. In combination with angiotensin 11, PGE₁, PGD₂, and 6_β-PG1₁, caused significant, dose-related attenuations of the angiotensin II vasoconstrictive response whereas PGE₂, PGF_2α, and U46619 potentiated the response. Injections of angiotensin II after the infusion of indomethacin into the fetal circulation resulted in a potentiation of angiotensin II induced vasoconstriction. The results indicate that prostaglandins exert their effects on the fetal-placental circulation by modulating the actions of angiotensin II.     

Endothelial cell apoptosis is induced by fetal plasma from pregnancy with umbilical placental vascular disease

OBJECTIVE: Vascular disease in the umbilical placental circulation that is detected by umbilical artery Doppler study is associated with adverse fetal outcome. Endothelial cell activation and platelet consumption are features of this pathologic condition. We postulated that this was due to the local release of factors that cause endothelial cell injury and that these would spill into the fetal circulation. To test this hypothesis, we examined for the presence in fetal plasma of factors that induced endothelial cell apoptosis in pregnancies that were complicated by umbilical placental vascular disease. STUDY DESIGN: Isolated and cultured human umbilical vein endothelial cells were exposed to fetal plasma from the 3 fetal groups: normal pregnancy (n = 32 patients), pregnancy with umbilical placental vascular disease that was identified by an abnormal umbilical artery Doppler study (n = 38 patients), and pregnancy with maternal preeclampsia and normal umbilical artery Doppler study (n = 16 patients). Early apoptosis can be recognized by a loss of plasma membrane asymmetry with membrane uptake of annexin V. This was measured with annexin V and propidium iodide staining by fluorescent-activated cell scanning. Cells that underwent early apoptosis stained positive for annexin V and negative for propidium iodide (in contrast with cells that underwent necrosis). Cytosolic proteolytic activity was also measured. The lysates from endothelial cells that were stimulated by fetal plasma from umbilical placental vascular disease were tested for caspase-3 and caspase-8 activities by a fluorescent assay with spectrofluorophotometry. RESULTS: The percentage of endothelial cells that underwent apoptosis was significantly higher (P <.05) when stimulated with fetal plasma from pregnancies with umbilical placental vascular disease (17.71% +/- 1.31%) than with fetal plasma from normal pregnancies (9.76% +/- 0.87%). In the presence of maternal preeclampsia with normal umbilical artery Doppler study, the percent of apoptotic cells (11.31% +/- 1.59%) was similar to that of the normal group. In the group with abnormal umbilical artery Doppler study, there was no difference between pregnancies with preeclampsia (n = 17 pregnancies) and without preeclampsia (n = 21 pregnancies). The protease activity of caspase-3 was significantly enhanced in the group with umbilical placental vascular disease compared with normal pregnancy (0.79 +/- 0.06 vs 0.45 +/- 0.08 microMol/L). However, no difference in caspase-8 activity was detected (0.66 +/- 0.05 vs 0.56 +/- 0.05 microMol/L). CONCLUSION: Endothelial cell apoptosis is a feature of umbilical placental vascular disease. Our study demonstrates the presence of factors in the fetal plasma that caused endothelial cells to undergo early apoptosis. This increased apoptosis was only seen in the presence of placental vascular disease and was independent of the presence or absence of maternal preeclampsia. Our results indicate that programmed endothelial cell death occurs in the fetal circulation as a part of the injury that is associated with the development of umbilical placental vascular disease. The caspase-3, rather than caspase-8, signal transduction pathway appears to be involved in the mediation of endothelial cell apoptosis that was detected in our study.