RESUMO
OBJECTIVE: To investigate the effects of syncytiotrophoblast microvillous membranes (STBM) in concentrations, found in vivo in women with pre-eclampsia, on endothelial function in isolated resistance arteries. SETTING: Department of Obstetrics and Gynaecology, Huddinge University Hospital, Stockholm. SAMPLE: Twenty-nine myometrial resistance arteries isolated from biopsies of healthy term pregnant women, obtained during caesarean section. METHODS: The myometrial arteries were mounted in a pressure arteriograph and perfused intraluminally for three hours with STBM (20 to 2000ng/mL) or with erythrocyte membranes or physiological salt solution as controls, all substituted with 0.5% bovine serum albumin. Bradykinin concentration-response curves were performed before and after perfusion. MAIN OUTCOME MEASURES: The bradykinin concentrationresponse curves were fitted to the Hill equation and maximal dilation and the pEC50 values were determined from these fits. Differences within groups were analysed with a paired Student's t test. Electron microscopic evaluation of the endothelium was performed. RESULTS: Neither STBM nor erythrocyte membrane perfusion affected maximal dilation or the pEC50 values of the bradykinin concentration-response curves at any concentration. Examination by electron microscopy showed no obvious damage to the endothelium after perfusion with STBM or erythrocyte membranes. CONCLUSION: Perfusion with STBM in concentrations up to 100 times those reported in pre-eclampsia has no significant effect on bradykinin-mediated dilation in isolated myometrial arteries.
Assuntos
Miométrio/irrigação sanguínea , Gravidez/fisiologia , Trofoblastos/fisiologia , Adulto , Artérias/fisiologia , Bradicinina/farmacologia , Endotélio Vascular/fisiologia , Feminino , Humanos , Microvilosidades/fisiologia , Miométrio/ultraestrutura , Pré-Eclâmpsia/etiologia , Pré-Eclâmpsia/patologia , Pré-Eclâmpsia/fisiopatologia , Resistência VascularRESUMO
OBJECTIVE: Preeclampsia is a syndrome involving dysfunction of vascular endothelium and imbalance between endothelium derived constricting and relaxing factors. Recent evidence suggests that endothelium-derived nitric oxide (NO) plays a role in the regulation of vascular resistance during normal pregnancy and preeclampsia. NO is a potent vasodilator and is generated by the catalytic action of nitric oxide synthases ecNOS and iNOS in myometrium and placenta. METHODS: In this study mRNA expressions of ecNOS and iNOS were compared in myometrium and placenta. Biopsies were collected from women with preeclampsia (n=8) and normal pregnancies (n=12). ecNOS and iNOS mRNA levels were determined using RT-PCR and expressed as arbitrary units after correction for control GAPDH gene mRNA levels. RESULTS: The mRNA expression of ecNOS was significantly higher in both myometrium (p<0.05) and placenta (p<0.05) from women with preeclampsia compared to that in normal pregnancies, while the iNOS mRNA level was not altered in myometrium and lower in placenta (p<0.05) from women with preeclampsia. CONCLUSIONS: The higher ecNOS mRNA expression might be a compensatory response to an impaired vasodilatation in the uteroplacental circulation during preeclampsia. Whether the similar and reduced levels of iNOS mRNA expression in myometrium and placenta, respectively, in women with preeclampsia is of importance remains to be further evaluated.
Assuntos
Miométrio/enzimologia , Óxido Nítrico Sintase/genética , Placenta/enzimologia , Pré-Eclâmpsia/enzimologia , RNA Mensageiro/análise , Adulto , Biópsia , Feminino , Expressão Gênica , Gliceraldeído-3-Fosfato Desidrogenases/genética , Humanos , Óxido Nítrico Sintase Tipo II , Óxido Nítrico Sintase Tipo III , Gravidez , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
OBJECTIVE: The aim of the present study was to compare the mRNA expression of endothelin-1 (ET-1), ET-1 receptors ET(A) and ET(B) in myometrium and placenta obtained from biopsies collected from women with preeclampsia (n=10) or normal pregnant (n=12). METHODS: The mRNA levels of ET-1 ET(A) and ET(B) were determined using RT-PCR and expressed as arbitrary units after correction for control GAPDH gene mRNA levels. RESULTS: The mRNA levels of ET-1 in myometrium and placenta were not altered in women with preeclampsia compared to normal pregnant. The mRNA expression of ET(A) was significantly reduced (p<0.05) in both placenta and myometrium from women with preeclampsia. The mRNA levels of ET(B) were similar in placentas from both preeclamptic and normal pregnant women, but higher in myometrium (p<0.05) from women with preeclampsia. CONCLUSIONS: These results indicate that the higher levels of ET-1 seen in preeclamptic women do not depend on an altered mRNA transcription of ET-1. The significantly reduced mRNA expression of ET(A) receptor in myometrium and placenta in women with preeclampsia might represent downregulation of the receptors due to the increased levels of ET-1 in uteroplacental circulation in this disorder. Much more research is needed before the role of ET(B) receptors in preeclampsia can be clarified.
Assuntos
Miométrio/química , Placenta/química , Pré-Eclâmpsia/metabolismo , Receptores de Endotelina/genética , Adulto , Endotelina-1/metabolismo , Feminino , Expressão Gênica , Humanos , Miométrio/metabolismo , Placenta/metabolismo , Gravidez , RNA Mensageiro/análise , Receptor de Endotelina A , Receptor de Endotelina B , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
OBJECTIVE: We sought to compare flow-mediated dilatation and myogenic and norepinephrine-induced tone in myometrial resistance arteries from women with preeclampsia and healthy pregnant women and to evaluate the role that nitric oxide may play in these responses. STUDY DESIGN: Arteries (approximately 200 microm, at 50 mm Hg) were dissected from myometrial biopsy specimens from women undergoing emergency cesarean delivery because of preeclampsia (n = 6) and from healthy control subjects undergoing planned cesarean delivery (n = 9). Responses to intraluminal flow, pressure, and a constrictor agonist (norepinephrine, 10(-6) mol/L) were studied in the absence and presence of the nitric oxide synthase inhibitor N omeganitro-L -arginine (10(-4) mol/L). Myogenic and norepinephrine-induced tone were calculated after the determination of artery diameter in the absence of extracellular calcium and in the presence of papaverine (10(-4) mol/L). RESULTS: An increase in intraluminal flow led to dilatation of isolated myometrial arteries from healthy gravid women, whereas flow-mediated dilatation was absent in arteries from gravid patients with preeclampsia (increase in diameter at maximum flow rate of 204 microL/min, 28% +/- 5% in healthy gravid patients vs -15% +/- 6% in gravid women with preeclampsia; analysis of variance, P <.05). Addition of N omega-nitro-L -arginine had no significant effect on flow-mediated responses in arteries from women with preeclampsia, whereas flow-mediated dilatation was abolished after addition of N omega-nitro-L -arginine in arteries from healthy gravid women (increase in diameter at a maximum flow rate of 204 microL/min, 28% +/- 5% control vs -9% +/- 5% N omega-nitro-L -arginine; analysis of variance, P <.05). Arteries from women with preeclampsia developed pressure-induced myogenic and norepinephrine-induced tone, similar to that obtained in arteries from healthy gravid women. In arteries from gravid women with preeclampsia, inhibition of nitric oxide synthase enhanced myogenic-induced tone (25% +/- 4% control vs 35% +/- 5% N omega-nitro-L -arginine; P <.05) and norepinephrine-induced tone (36% +/- 4% control vs 46% +/- 6% N omega-nitro-L -arginine; P <.05), as in arteries from healthy gravid women. CONCLUSIONS: Nitric oxide may participate in modulation of pressure- and norepinephrine-induced tone even in preeclampsia, but the shear stress-mediated release of nitric oxide is absent. Failure of shear stress-mediated dilation in myometrial arteries from gravid women with preeclampsia might contribute to the impaired uteroplacental blood flow in this disease.
Assuntos
Óxido Nítrico/sangue , Pré-Eclâmpsia/fisiopatologia , Reologia , Útero/irrigação sanguínea , Adulto , Artérias/fisiopatologia , Velocidade do Fluxo Sanguíneo , Cesárea , Inibidores Enzimáticos/farmacologia , Feminino , Humanos , Técnicas In Vitro , Músculo Liso Vascular/fisiopatologia , Miométrio/irrigação sanguínea , Óxido Nítrico Sintase/antagonistas & inibidores , Nitroarginina/farmacologia , Norepinefrina/farmacologia , Gravidez , Pressão , VasodilataçãoRESUMO
OBJECTIVE: We evaluated the role of endothelium-derived nitric oxide and endothelin 1 in the modulation of myogenic tone, norepinephrine-induced tone, and flow-mediated responses in resistance arteries from pregnant women at term. STUDY DESIGN: Arteries (approximately 200 microm at 50 mm Hg; n = 27) were dissected from myometrial biopsies obtained from women undergoing elective cesarean delivery at term and mounted in a pressure arteriograph. Responses to intraluminal flow, pressure, and norepinephrine were studied in the absence and presence of the nitric oxide synthase inhibitor Nomega-nitro-L-arginine and the endothelin-converting enzyme inhibitor phosphoramidon. RESULTS: Pressure-induced (80 mm Hg) myogenic tone was significantly enhanced after incubation with Nomega-nitro-L-arginine (33% +/- 8% vs 24% +/- 4%; P <.05), whereas phosphoramidon significantly reduced myogenic tone (24% +/- 5% vs 33% +/- 5%; P <.05). A combination of Nomega-nitro-L -arginine and phosphoramidon did not affect myogenic tone. Norepinephrine-induced tone was significantly enhanced after nitric oxide synthase inhibition (49% +/- 6% vs 41% +/- 5%; P <.05) but was not affected by phosphoramidon. Flow-mediated dilatation was increased in the presence of phosphoramidon compared with flow-induced dilatation in physiologic salt solution (maximum dilatation, 57% +/- 12% vs 30% +/- 5%; analysis of variance, P <.05), and all flow-induced dilatation was abolished by Nomega-nitro-L -arginine. CONCLUSIONS: Nitric oxide and endothelin 1 may play a significant role in modulation of myogenic tone and flow-mediated responses in the resistance vasculature of the uterine circulation in normal pregnancy.
Assuntos
Artérias/efeitos dos fármacos , Endotelina-1/farmacologia , Miométrio/irrigação sanguínea , Óxido Nítrico/farmacologia , Resistência Vascular , Artérias/fisiologia , Velocidade do Fluxo Sanguíneo , Cesárea , Inibidores Enzimáticos/farmacologia , Feminino , Hemorreologia , Humanos , Técnicas In Vitro , Óxido Nítrico Sintase/antagonistas & inibidores , Nitroarginina/farmacologia , Norepinefrina/farmacologia , Gravidez , Pressão , Reprodutibilidade dos Testes , VasodilataçãoRESUMO
OBJECTIVE: Our purpose was to evaluate flow-induced responses, myogenic tone, and norepinephrine-induced constriction in myometrial resistance arteries from normal term pregnant women and the role that nitric oxide and prostanoids may play in these responses. STUDY DESIGN: Arteries (approximately 200 microns, n = 14, at 40 mm Hg) were dissected from myometrial biopsy specimens from women undergoing cesarean section and then were mounted in a pressure arteriograph. Responses to intraluminal flow, pressure, and a constrictor agonist (norepinephrine 10(-6) mol/L) were studied in the absence and presence of N omega-nitro-L-arginine methyl ester (n = 7) or indomethacin (n = 5). Myogenic and norepinephrine-induced tone were calculated after the determination of artery diameter in the absence of extracellular calcium. RESULTS: Arteries developed myogenic tone (80 mm Hg) that was not modulated by nitric oxide or prostanoid release, whereas norepinephrine-induced tone was significantly enhanced by the nitric oxide inhibitor. An increase in intraluminal flow led to dilatation in physiologic salt solution and indomethacin, but to constriction in the presence of N omega-nitro-L-arginine methyl ester (percent increase in diameter at flow rate of 184.6 microliters/min, 24% +/- 8% in physiologic salt solution and 20% +/- 4% in the presence of indomethacin versus -27% +/- 12% in N omega-nitro-L-arginine methyl ester alone and -21% +/- 10% in indomethacin and N omega-nitro-L-arginine methyl ester, respectively, analysis of variance, p < 0.05). CONCLUSIONS: Flow-induced shear stress is a physiologic modulator of vascular tone in myometrial arteries from pregnant women. Nitric oxide, but not prostanoids, mediates this response and also blunts norepinephrine constriction. Nitric oxide may play a fundamental role in the maintenance of adequate blood supply to the fetus during human pregnancy.
Assuntos
Miométrio/irrigação sanguínea , Óxido Nítrico/fisiologia , Gravidez/fisiologia , Artérias/fisiologia , Feminino , Humanos , NG-Nitroarginina Metil Éster/farmacologia , Norepinefrina/farmacologia , Perfusão , Estresse Mecânico , Vasodilatação/efeitos dos fármacosRESUMO
OBJECTIVE: Our purpose was to compare myometrial and omental resistance arteries from term pregnant women with respect to myogenic behavior in the presence or absence of a nitric oxide synthase inhibitor and to compare distensibility and acetylcholine-mediated dilatation in these vessels. STUDY DESIGN: Intramyometrial (n = 17) and omental (n = 14) resistance arteries from term normal pregnant women were studied in a pressurized arteriograph system. Myogenic tone was evaluated during increments in intraluminal pressure from 20 to 120 mm Hg with and without inhibition of nitric oxide synthase. Endothelium-dependent relaxation was assessed by evaluating the response to acetylcholine (10(-6) mol/L) in arteries pressurized at 70 mm Hg. RESULTS: Myogenic tone was greater at all pressure steps in the myometrial than in the omental arteries (p < 0.05). Inhibition of nitric oxide synthase with N(omega)-nitro-L-arginine had no influence on myogenic tone in either group. Relaxation to acetylcholine was greater in myometrial (18% +/- 4%) compared with omental vessels (7% +/- 2%, p < 0.05). The passive distensibility (Ca++-free solution and in the presence of papaverine) of arteries from the myometrium and the omentum was similar. CONCLUSION: Normal pregnancy is associated with different mechanical properties of resistance vessels from the two vascular beds studied. Basal nitric oxide release does not modify myogenic tone, at least under no-flow conditions. Acetylcholine-induced relaxation is greater in myometrial than in omental arteries.
Assuntos
Miométrio/irrigação sanguínea , Omento/irrigação sanguínea , Resistência Vascular , Acetilcolina/farmacologia , Feminino , Humanos , Trabalho de Parto , Óxido Nítrico Sintase/antagonistas & inibidores , Gravidez , Terceiro Trimestre da Gravidez , Pressão , Resistência Vascular/efeitos dos fármacosRESUMO
OBJECTIVE: To compare the effect of endothelin on isolated resistance arteries from different vascular beds in normal and preeclamptic women before and after pretreatment with the ETA receptor antagonist BQ-123. MATERIALS AND METHODS: Resistance arteries from myometrial and omental biopsies obtained at cesarean section of normal pregnant and preeclamptic women were dissected and mounted in organ baths for recording of isometric tension. The contractile response to endothelin-1 in presence and absence of BQ-123 was recorded. RESULTS: Endothelin-1 induced similar concentration-dependent contractions in all arteries investigated. In women with preeclampsia the contractile response induced by endothelin-1 was significantly higher in omental as compared to myometrial vessels. Pretreatment with BQ-123 significantly shifted the concentration-response curve to the right but only reduced the maximum contractile response in omental vessels. CONCLUSION: Endothelin-1 is a potent constrictor of resistance arteries from different vascular beds in normal pregnancy and preeclampsia. The contractile effect is at least in part mediated by ETA receptors, since it was significantly reduced after pretreatment with BQ-123. In preeclamptic but not in normal pregnant women the response to endothelin-1 was reduced in myometrial as compared to omental arteries, possibly secondary to receptor down regulation.
Assuntos
Artérias/fisiologia , Endotelinas/fisiologia , Peptídeos Cíclicos/fisiologia , Pré-Eclâmpsia/metabolismo , Gravidez/fisiologia , Receptores de Endotelina/fisiologia , Adulto , Biópsia , Cesárea , Procedimentos Cirúrgicos Eletivos , Feminino , Humanos , Consentimento Livre e Esclarecido , Miométrio/irrigação sanguínea , Omento/irrigação sanguíneaRESUMO
In the present in vitro study we investigated the possible vasorelaxing effect of atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (cGMP) on small intramyometrial arteries precontracted by endothelin-1 (ET-1). Myometrial biopsies from normotensive pregnant women were obtained during cesarean section and arteries of resistance vessel size were dissected and mounted in a tissue chamber for isometric registration of contractile tone. In arteries preconstricted with ET-1 (10(-8)M), ANP produced a concentration-dependent relaxation of 19 +/- 5% (mean +/- SEM) and 27 +/- 7% at concentrations of 10(-7) and 3 x 10(-7) M, respectively. cGMP induced a relaxation of 13 +/- 2, 18 +/- 3, 25 +/- 4 and 30 +/- 7% at concentrations of 10(-5), 10(-4), 3 x 10(-4) and 10(-3) M, respectively. Pretreatment with ANP did not attenuate the contraction produced by ET-1. We suggest that ANP may have a vasodilating effect on preconstricted human uteroplacental vessels. It also provides evidence for the role of other endogenous or exogenous vasodilators acting via cGMP-dependent mechanisms in the counteraction of ET-1-induced contraction of the myometrial resistance vessels during pregnancy.
Assuntos
Artérias/efeitos dos fármacos , Fator Natriurético Atrial/farmacologia , GMP Cíclico/farmacologia , Endotelinas/farmacologia , Miométrio/irrigação sanguínea , Artérias/fisiologia , Cesárea , Feminino , Humanos , Gravidez , Vasoconstrição/efeitos dos fármacos , Vasodilatação/efeitos dos fármacosRESUMO
The results of our previous studies suggested that endothelin-1 (ET-1) might be contributory to the impaired uteroplacental blood flow seen in preeclampsia. The aim of this study was to investigate the in vitro influence of isradipine on ET-1-induced contraction of myometrial resistance arteries from pregnant women, as these vessels are partly responsible for the regulation of uteroplacental blood flow in preeclampsia. Small myometrial arteries were dissected from myometrium obtained from 20 normotensive term pregnant women undergoing elective cesarean section and mounted in a tissue chamber. Tension was recorded isometrically. When ET-1 (10(-8) mol/L)-contracted vessels were exposed to increasing concentrations (10(-6), 10(-5), and 10(-4) mol/L) of isradipine, the myometrial arteries demonstrated essentially no relaxation. A significant mean relaxation of 31% was seen only with the highest isradipine concentration of 10(-3) mol/L. Pretreatment with isradipine attenuated ET-1-induced contraction by 26% at 3 x 10(-4) mol/L and by up to 80% at 10(-3) mol/L. Preincubation with lower concentrations of isradipine did not significantly reduce subsequent ET-1 contraction. The present study has thus shown that isradipine at high concentrations counteracts ET-1-induced constriction of myometrial arteries in term pregnant women. Pretreatment with isradipine at high concentrations attenuates the ET-1 contraction.