Human Placental Veins Research Articles

Pharmacological inhibition of the F1 -ATPase/P2Y1 pathway suppresses the effect of apolipoprotein A1 on endothelial nitric oxide synthesis and vasorelaxation.

The contribution of apolipoprotein A1 (APOA1), the major apolipoprotein of high-density lipoprotein (HDL), to endothelium-dependent vasodilatation is unclear, and there is little information regarding endothelial receptors involved in this effect. Ecto-F1 -ATPase is a receptor for APOA1, and its activity in endothelial cells is coupled to adenosine diphosphate (ADP)-sensitive P2Y receptors (P2Y ADP receptors). Ecto-F1 -ATPase is involved in APOA1-mediated cell proliferation and HDL transcytosis. Here, we investigated the effect of lipid-free APOA1 and the involvement of ecto-F1 -ATPase and P2Y ADP receptors on nitric oxide (NO) synthesis and the regulation of vascular tone. Nitric oxide synthesis was assessed in human endothelial cells from umbilical veins (HUVECs) and isolated mouse aortas. Changes in vascular tone were evaluated by isometric force measurements in isolated human umbilical and placental veins and by assessing femoral artery blood flow in conscious mice. Physiological concentrations of lipid-free APOA1 enhanced endothelial NO synthesis, which was abolished by inhibitors of endothelial nitric oxide synthase (eNOS) and of the ecto-F1 -ATPase/P2Y1 axis. Accordingly, APOA1 inhibited vasoconstriction induced by thromboxane A2 receptor agonist and increased femoral artery blood flow in mice. These effects were blunted by inhibitors of eNOS, ecto-F1 -ATPase and P2Y1 receptor. Using a pharmacological approach, we thus found that APOA1 promotes endothelial NO production and thereby controls vascular tone in a process that requires activation of the ecto-F1 -ATPase/P2Y1 pathway by APOA1. Pharmacological targeting of this pathway with respect to vascular diseases should be explored.

The Role of VEGF Pathways in Human Physiologic and Pathologic Angiogenesis

In preclinical models, VEGF is a potent stimulant of both physiologic and pathologic angiogenesis. Conversely, anti-VEGF regimens have successfully inhibited angiogenesis both in vitro and in vivo. We hypothesized that VEGF would stimulate both physiologic and pathologic angiogenesis in a human-based fibrin-thrombin clot angiogenesis assay. We further speculated that anti-VEGF regimens would inhibit angiogenesis in this assay. To test these hypotheses, discs of human placental veins (physiologic model) and fragments of human tumors (pathologic model) were embedded in fibrin-thrombin clots and treated with either VEGF-A165 (VEGF) or anti-VEGF pathway reagents including bevacizumab, IMC-18F1, IMC-1121, and PTK787 (n=30 wells per treatment group, multiple concentrations tested in each specimen). Angiogenic responses were assessed visually using a previously validated grading scheme. The percent of tissue explants that developed angiogenic invasion into the clot (% I) as well as the extent of angiogenic growth (AI) via a semi-quantitative scale were assessed at set intervals. VEGF failed to stimulate angiogenesis in both the physiologic and the pathologic model. While anti-VEGF reagents that targeted only one element of the VEGF pathway failed to consistently inhibit angiogenesis, PTK787, a receptor tyrosine kinase inhibitor that targets multiple VEGF and non-VEGF receptors, profoundly inhibited both physiologic and pathologic angiogenesis. These results suggest that VEGF-related pathways may not be solely responsible for stimulating angiogenesis in humans. Targeting the VEGF pathway in combination with elements of other growth factor pathways may provide a more effective means of inhibiting angiogenesis than targeting VEGF alone.

Vasomotion in Human Umbilical and Placental Veins: Role of Gap Junctions and Intracellular Calcium Reservoirs in Their Synchronous Propagation

Vasomotion was characterized using human placentae vessel rings; force displacement transducers recorded isometric contractions. Umbilical vein rings display rhythmic contractions occurring with a frequency of 1.47 ± 0.01 min −1 and 274 ± 2.2 mg ( n = 211) of amplitude, which corresponds to 11.1 ± 0.4% of the maximal KCl contracture. Vasomotion waves were recorded for up to 8 h; their amplitude and duration was larger in umbilical veins than arteries or chorionic vessels ( p < 0.001), vasomotion frequency was indistinguishable among these vessels. Segments of the umbilical vein closer to the fetus showed larger amplitudes and longer-lasting waves. Gap junction blockers, including peptide Gap 27, 18α-glycyrrhetinic acid, hexanol, heptanol or octanol, reduced the amplitude but not the frequency of vasomotion; all these drugs, in addition, decreased tissue basal tension. The role of intracellular calcium stores was evidenced using calcium-free buffer, which reduced oscillation amplitude and tissue basal tension. Cyclopiazonic acid increased wave amplitude and tissue basal tension, reducing oscillatory frequency. We propose that biological oscillators localized in the smooth muscle layer of the umbilical cord, trigger vasomotion waves, which are synchronized and propagated via gap junctions; internal calcium reservoirs are essential for their maintenance. These myogenic oscillations may be relevant for maternal-fetus blood flow and contribute to fetal nutrition and development.

Nitric oxide enhances the contraction to prostaglandin F2α in human placental veins

Nitric oxide enhances the contraction to prostaglandin F2α in human placental veins

Comparative study of sodium nitroprusside induced vasodilation of human placental veins from premature and full-term normotensive and preeclamptic pregnancy

The objective of this study was to determine whether nitrovasodilator (nitric oxide donor) drug induced relaxation is different between preeclamptic and normotensive pregnancy. Human placental veins were collected at the time of delivery from normotensive (n = 6 premature, n = 6 full term) and preeclamptic (n = 6 premature, n = 3 full term) women and cut into rings. Cumulative concentration-response curves were performed on 5-hydroxytryptamine-contracted rings for the nitrovasodilator agent, sodium nitroprusside (SNP). The EC50 values were determined from the SNP concentration-response curves of the individual subjects, and were compared across gestational age and between preeclamptic and normotensive pregnancy by two-way ANOVA. There was no difference in the SNP EC50 values for normotensive and preeclamptic human placental veins in either the premature or full-term study groups. However, for both normotensive and preeclamptic pregnancy, the SNP EC50 value for full-term placental vein was greater than that for premature tissue. The sensitivity of human placental veins to SNP is similar between preeclamptic and normotensive pregnancy at similar gestational ages, but is increased in premature compared with full-term pregnancy in both preeclamptic and normotensive pregnant women.

Does endothelium-independent relaxation to acetylcholine exist in human umbilical and placental arteries and veins?

Does endothelium-independent relaxation to acetylcholine exist in human umbilical and placental arteries and veins?

Properties of a progesterone-induced relaxation in human placental arteries and veins

Properties of a progesterone-induced relaxation in human placental arteries and veins

Properties of a progesterone-induced relaxation in human placental arteries and veins.

To study the effects of progesterone on placental vascular tone, we used isolated (1-2 mm in diameter) placental arteries and veins from term uncomplicated pregnancies. These vessels, incubated in Krebs buffer (pH 7.4) under 5% O2-5% CO2 (balance N2, PO2 approximately 35 torr) and precontracted with serotonin were exposed to incremental doses of progesterone (0.01-30 mumol/L) in the presence or absence of endothelium, 10 mumol/L indomethacin (inhibits prostaglandin synthesis), 10 mumol/L methylene blue (a soluble guanylate cyclase inhibitor), 100 mumol/L nitro-L-arginine (inhibits L-arginine metabolism), 1 mmol/L isobutylmethylxanthine (a cAMP phosphodiesterase inhibitor), or 30 mumol/L mifepristone (RU 38486, an antiprogestin). Progesterone elicited an acute dose-dependent relaxation in both arteries and veins that was not altered by removal of the endothelium or pretreatment with indomethacin, nitro-L-arginine, or methylene blue, excluding a role for prostaglandins, L-arginine products, or cGMP in mediating this relaxation. However, isobutylmethylxanthine significantly enhanced the relaxation in response to progesterone, suggesting a role for cAMP. RU 38486 inhibited the relaxation by 50-100%, depending on the progesterone dose, consistent with a role for progesterone receptors. These results suggest that progesterone causes a dose-dependent endothelium-independent relaxation of human placental arteries and veins. This relaxation seems to be mediated by a receptor-activated cAMP mechanism and could be physiologically important in maintaining low resistance and adequate blood flow in the placental circulation.

Effects of ANP on human placental arteries and veins in vitro

Effects of ANP on human placental arteries and veins in vitro

Gestational diabetes impairs relaxation of human placental veins to H 2O 2 and lactate : [formula omitted], E. Martinez X, R.P. Fayngersh x, H. Jiang X, N. Tejani, M.S. Wolin x. Depts of Physiology and Obs-Gyn, New York Medical College, Valhalla, NY

Gestational diabetes impairs relaxation of human placental veins to H 2O 2 and lactate : [formula omitted], E. Martinez X, R.P. Fayngersh x, H. Jiang X, N. Tejani, M.S. Wolin x. Depts of Physiology and Obs-Gyn, New York Medical College, Valhalla, NY

Endothelial Modulation of the Vascular Sodium Pump

Endothelial interference with ouabain effects on vascular smooth muscle was analyzed in isolated human placental arteries and veins, carotid arteries from reserpinized guinea pigs (to eliminate the adrenergic actions of the glycoside), and aorta from Wistar-Kyoto (WKY) rats that were 5 weeks, 3, 6, 12, and 18 months old. After endothelium removal, ouabain-evoked contractions were increased in human placental vessels and guinea pig carotid arteries. These effects were not mimicked by the blockade of nitric oxide, prostaglandin, or leukotriene synthesis. Bioassay experiments suggest the release of an endothelial diffusable factor(s). 86Rb+ uptake, a method to measure sodium-pump activity, was significantly reduced by the removal of endothelium. In aortas from WKY rats, ouabain caused contractions that were increased with the age of animals until 12 months. Endothelium removal increased ouabain effects in vessels from animals of 3 and 6 months but not in older ages. These results suggest (a) that there is an inhibitory endothelial modulation of ouabain-induced vasoconstriction by the release of a diffusible factor(s); (b) that this substance is not related to nitric oxide, prostaglandins, or leukotrienes; (c) that its mechanism of action could be stimulating the activity of vascular sodium pump and/or antagonizing its inhibition by ouabain; and (d) that the endothelial modulation is lost in the elderly.

Role of extracellular calcium and calcium channels in response of human placental venous smooth muscle to endothelin-1

Our purpose was to evaluate the role of calcium and calcium channels in endothelin-1-induced contraction of the smooth muscle of human placental veins. Placentas were collected after vaginal delivery at term. After their removal from the chorionic plate, placental veins were divided into rings that were suspended in organ chambers and stretched to optimal tension. In the first part of the study, vessels from six women were initially suspended in calcium-poor modified Krebs-Ringer solution. They were then treated with either EGTA [ethylene glycol-bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid; calcium chelator, 0.5 mmol/L] or calcium chloride 2.5 mmol/L (control). Endothelin-1 was then added cumulatively (10(-10) to 10(-7) mol/L), and the resulting changes in isometric tensions were recorded. In the second part of the study vessels from six other women were treated with either (1) normal modified Krebs-Ringers solution (control), (2) calcium-poor modified Krebs-Ringers solution, or (3) nicardipine (dihydropyridine calcium channel inhibitor, 10(-7) mol/L) in separate organ chambers. Endothelin-1 was then added cumulatively. Endothelin-1 produced concentration-dependent contractions in placental veins, with maximal tension reached at 10(-7) mol/L. Substitution of calcium-poor for standard Krebs-Ringers solution in the organ chamber abolished contractions to low endothelin-1 concentrations (< or = 10(-9) mol/L, p < 0.001) but did not affect the contractile response to higher concentrations. EGTA abolished contractions to all concentrations tested (p < 0.02). Nicardipine significantly, but incompletely, inhibited the contractile responses to all endothelin-1 concentrations tested (p < 0.05). Endothelin-1 induces contraction of the smooth muscle of human placental veins, which requires the influx of extracellular calcium. Dihydropyridine-sensitive calcium channels represent a major route of entry, but other pathways participate. The fetal effects of nifedipine and other calcium-channel blockers deserve specific evaluation in intrauterine growth retardation and other pregnancies complicated by elevated fetal levels of endothelin-1.

Contractile effect of endothelin in human placental veins: Role of endothelium prostaglandins and thromboxane

The aim was to study the effects of endothelin-1 on human placental veins and the role of cyclooxygenase products as mediators of these effects. Rings of placental veins with and without endothelium were suspended in organ chambers filled with physiologic salt solution. After a period of stabilization at optimal basal tension, isometric tensions in the control group were recorded at increasing concentrations of endothelin-1 (10(-10) to 10(-7) mol/L). Rings in the experimental groups were treated with either indomethacin (cyclooxygenase inhibitor, 10(-5) mol/L), dazoxiben (thromboxane synthetase inhibitor, 10(-4) mol/L), or SQ29548 (thromboxane receptor antagonist, 10(-6) mol/L) before addition of endothelin-1. To demonstrate the presence of functional thromboxane receptors in the rings, contractile responses to U-46619 (10(-9) to 10(-6) mol/L), a thromboxane A2 analog were measured. The effectiveness of SQ29548 blockade was tested in rings treated with SQ29548 (10(-6) mol/L) before addition of U-46619. The concentration-response curves of the treated and control groups were compared with the Student paired t test. Endothelin-1 in doses of 10(-10) to 10(-7) mol/L caused concentration-dependent contraction of placental veins. Indomethacin significantly reduced the response of veins with endothelium to low endothelin-1 concentrations (10(-9.5) to 10(-9) mol/L), (p < 0.05). However, it had no effect at higher endothelin-1 concentrations or in vessels without endothelium. The presence of functional thromboxane A2 receptors was confirmed by the vasoconstrictor effect of U-46619 and its blockade by treatment with SQ29548. Neither SQ29548 nor the thromboxane A2 synthesis inhibitor dazoxiben significantly influenced the response to endothelin-1. These results demonstrated that endothelin-1 is a potent vasoconstrictor in the human placental vein. Although functional thromboxane A2 receptors exist in this vessel, endothelin-1's action is independent of thromboxane A2. Prostaglandins may mediate part of the endothelin-1-induced placental vasoconstriction. However, endothelin-1 acts primarily by a direct effect on vascular smooth muscle cells.

Hydrogen peroxide and reoxygenation cause prostaglandin-mediated contraction of human placental arteries and veins

Hydrogen peroxide and reoxygenation cause prostaglandin-mediated contraction of human placental arteries and veins

Endothelins 1 and 3 and big endothelin-1 contract isolated human placental veins.

Experiments were designed to investigate the reactivity of vascular smooth muscle to endothelins (ETs) in veins taken from human placentas immediately after delivery. The placental veins were cut into rings and suspended between two stirrups in conventional organ chambers (filled with aerated, modified Krebs-Ringer bicarbonate solution) for isometric recording of tension. ET-1 and ET-3 caused concentration-dependent contractions of the isolated human placental veins. The responses induced by ET-1 were greater than those evoked by ET-3 and were not significantly affected by BQ-123, a selective inhibitor of ETA receptors. Contractions to big ET-1 were obtained in rings both with and without endothelium; they were inhibited by phosphoramidon, an inhibitor of endothelin-converting enzyme. These findings indicate that the conversion of the precursor of ET-1 can occur in human placental veins. The receptors mediating the contraction of human placental veins to endothelins do not belong to the ETA subtype; the response to the peptides is probably mediated in part by an uncharacterized ET-receptor subtype and in part by ETB receptors. The output of big ET-1 in the vascular wall or from surrounding tissues in the placenta could be involved in the regulation of venous tone in this organ.

Sodium pump activation by 5-hydroxytryptamine in human placental veins

The aim of the present study was to determine the influence of the sodium pump on the responses elicited by 5-hydroxy tryptamine (5-HT) in segments of human placental veins. 5-HT (10−9−3 × 10−7M) elicited potent concentration-dependent vasoconstrictor responses, but a fall in tone was observed at higher concentrations. In the presence of 10−7 M ouabain, this fall in tension was abolished. A single concentration of 5-HT (10−6 M) produced a biphasic response, consisting in a fast early contraction followed by a slow relaxation. This relaxant phase was concentration dependently inhibited by ouabain (10−7 and 10−6 M), and abolished by preincubating the vessels in a K+-free solution and reducing bath temperature to 28°C, methods usually employed to inhibit the sodium pump. After adding 7.5 mM K+ or returning the temperature to 37°C, marked relaxation was observed. On the other hand, the relaxant phase with the amine remained unchanged by pretreatment with phenidone, oxyhemoglobin, indomethacin (all at 10−5 M) and endothelium removal. 5-HT (10−7 and 10−6M) elicited increases in ouabain-sensitivc 86Rb+ uptake. These results suggest that: (1) 5-HT activates Na+K+-ATPase, likely by an indirect mechanism that involves an increase of intracellular sodium concentration; and (2) the relaxant phase of 5-HT-evoked vasoactive responses is not mediated by the release of nitric oxide or prostacyclin from the endothelium.

334 Increases in O 2 Tension Appear to Cause Prostaglandin-Mediated Contraction of Human Placental Veins Via H 2O 2

334 Increases in O 2 Tension Appear to Cause Prostaglandin-Mediated Contraction of Human Placental Veins Via H 2O 2

Sodium pump activity and contractile effect of ouabain in human placental veins

The aim of the present study was to determine the number and affinity of [ 3H]ouabain binding sites, the sodium pump activity and the mechanisms involved in the contractile effects of ouabain in human placental veins. Scatchard analysis suggested the existence of a single population of binding sites with a K D of 196.7 nM and a B max of 1606 fmol/mg protein. The sodium pump activity was determined from the 86Rb + uptake, which was reduced concentration dependently by ouabain (10 −8–10 −4 M), and from the K + (7.5 mM)-induced relaxation in veins preincubated in a K +-free medium and precontracted with PGF 2α (10 −6 M), which was also blocked by the glycoside (10 −6 M). Ouabain (10 −7-10 −4 M) induced concentration-dependent contractions, which were not modified by either nifedipine or Bay K 8644 (10 −7 and 10 −6 M). Ca 2+ omission from the medium or amiloride (10 −4 M) inhibited these contractions, whereas monensin (10 −6 M) potentiated them. These data indicate that human placental veins possess sodium pump activity and that its inhibition by ouabain induces potent contractions mainly mediated by Ca 2+ entry through the Na +-Ca 2+ exchange system.

Interference of diltiazem with serotonin-and potassium-induced contractions in human placental veins

1. In segments of human placental veins precontracted with K + (25, 40 or 75 mM), diltiazem produced concentration-dependent relaxations with similar EC 50 values. 2. Diltiazem (20 min preincubations) also caused concentration-dependent inhibition of the contractions induced by K + (40 or 75 mM) and 5-HT (serotonin, 3 × 10 −7 M). IC 50 values were similar, in both cases. 3. The time-course of the vasocontractions induced by 75 mM K + and 3 × 10 −7 M 5-HT in the absence and in the presence of diltiazem were different. The contractions caused by K + were sustained and transient those elicited by 5-HT. 4. These data suggest that (1) this vasculature is sensitive to diltiazem, and (2) the Ca influx through voltage-operated Ca channels (activated by K +) and through receptor-operated Ca channels (activated by 5-HT) is very similar.

Prostacyclin and human foetal circulation

Tissues from human umbilical cord arteries and placental veins generated much greater prostacyclin activity than vessels from normal adults. High prostacyclin generation could contribute to maintaining the low peripheral vascular resistance typical of foetal circulation in which blood pressure is low despite very high cardiac output.