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Asif H, Barnett SD, Buxton ILO. Title: β3 Adrenergic Receptor Signaling in the Human Myometrium. Reprod Sci 2022; 30:124-134. [PMID: 35380411 PMCID: PMC8980516 DOI: 10.1007/s43032-022-00917-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 03/11/2022] [Indexed: 01/06/2023]
Abstract
Preterm labor leading to preterm birth is the leading cause of infant morbidity and mortality. Although β2 adrenergic agonists fail to provide adequate tocolysis, the expression of the β3 adrenergic receptor in myometrium and its unique signaling suggest a role for β3 agonist in the management of preterm labor. Western blot analysis showed that the β3 adrenergic receptor expression increased in human pregnancy myometrium compared to nonpregnant tissues (p < 0.0001). There was no difference in β3 adrenergic receptor expression throughout pregnancy (p > 0.05). The addition of the β3 agonist mirabegron in the tissue bath relaxed oxytocin contracted myometrium with an EC50 of 41.5 µM. Relaxation was partially blocked by the addition of the eNOS blocker Nω-nitro-L-arginine, or the large conductance potassium channel blocker paxilline. Combination of Nω-nitro-L-arginine and paxilline prevented mirabegron-mediated relaxation. Imaging revealed that the β3 adrenergic receptors are expressed by both myocyte and microvascular endothelial cells isolated from human myometrium. Nitric oxide production measured by 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate revealed that mirabegron stimulated nitric oxide production in myometrial endothelial cells. These data suggest that both endothelial and smooth muscle cells contribute to relaxation through disparate signaling pathways. Repurposing of approved medications tested in human myometrium as uterine tocolytics can advance prevention of preterm birth. These data argue that further examination of β3 adrenergic receptor signaling in myometrium may reveal mirabegron as a useful tocolytic in combination tocolysis regimens.
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Affiliation(s)
- Hazik Asif
- School of Medicine, Department of Pharmacology, Myometrial Function Laboratory, University of Nevada, Reno, NV 89557-0318 USA
| | - Scott D. Barnett
- School of Medicine, Department of Pharmacology, Myometrial Function Laboratory, University of Nevada, Reno, NV 89557-0318 USA
| | - Iain L. O. Buxton
- School of Medicine, Department of Pharmacology, Myometrial Function Laboratory, University of Nevada, Reno, NV 89557-0318 USA
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Guerra DD, Hurt KJ. Gasotransmitters in pregnancy: from conception to uterine involution. Biol Reprod 2020; 101:4-25. [PMID: 30848786 DOI: 10.1093/biolre/ioz038] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 02/14/2019] [Accepted: 03/06/2019] [Indexed: 12/13/2022] Open
Abstract
Gasotransmitters are endogenous small gaseous messengers exemplified by nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S or sulfide). Gasotransmitters are implicated in myriad physiologic functions including many aspects of reproduction. Our objective was to comprehensively review basic mechanisms and functions of gasotransmitters during pregnancy from conception to uterine involution and highlight future research opportunities. We searched PubMed and Web of Science databases using combinations of keywords nitric oxide, carbon monoxide, sulfide, placenta, uterus, labor, and pregnancy. We included English language publications on human and animal studies from any date through August 2018 and retained basic and translational articles with relevant original findings. All gasotransmitters activate cGMP signaling. NO and sulfide also covalently modify target protein cysteines. Protein kinases and ion channels transduce gasotransmitter signals, and co-expressed gasotransmitters can be synergistic or antagonistic depending on cell type. Gasotransmitters influence tubal transit, placentation, cervical remodeling, and myometrial contractility. NO, CO, and sulfide dilate resistance vessels, suppress inflammation, and relax myometrium to promote uterine quiescence and normal placentation. Cervical remodeling and rupture of fetal membranes coincide with enhanced oxidation and altered gasotransmitter metabolism. Mechanisms mediating cellular and organismal changes in pregnancy due to gasotransmitters are largely unknown. Altered gasotransmitter signaling has been reported for preeclampsia, intrauterine growth restriction, premature rupture of membranes, and preterm labor. However, in most cases specific molecular changes are not yet characterized. Nonclassical signaling pathways and the crosstalk among gasotransmitters are emerging investigation topics.
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Affiliation(s)
- Damian D Guerra
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado, USA
| | - K Joseph Hurt
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado, USA.,Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado, USA
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Gupta H, Deshpande SB. Bisphenol A decreases the spontaneous contractions of rat uterus in vitro through a nitrergic mechanism. J Basic Clin Physiol Pharmacol 2019; 29:593-598. [PMID: 29768248 DOI: 10.1515/jbcpp-2017-0068] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Accepted: 03/26/2018] [Indexed: 01/25/2023]
Abstract
BACKGROUND Bisphenol A (BPA), a chemical used in the manufacture of plastics, has toxic effects on various systems of the human body including the reproductive system. BPA possesses estrogenic activity and is implicated in altering oogenesis, ovulation, and fertility. In addition to ovulatory changes, uterine contractility is an important factor for fertility. However, the effects of BPA on myometrial contractions are not known. Therefore, we examined the effect of BPA on rat uterine contractions. METHODS The uterus was isolated from adult rats showing estrous phase, and spontaneous in vitro contractions were recorded (35±1 °C). The effect of cumulative concentrations of BPA was determined. Further, the involvement of nitric oxide (NO) and guanylyl cyclase (GC) for the BPA-induced changes on uterine contractility was evaluated using the NO synthase inhibitor (L-NAME) or GC inhibitor (methylene blue). RESULTS BPA decreased the amplitude and frequency of spontaneous uterine contractions in a concentration-dependent manner. A decrease of 50% occurred at 1 and 3 μM for amplitude and frequency, respectively. L-NAME (N-ω-nitro-l-arginine methyl ester) blocked the BPA-induced decrease in amplitude at all concentrations but antagonized the frequency only at the maximum concentration (10 μM). Methylene blue (a GC inhibitor) did not block the BPA-induced responses but for the frequency at 10 μM of BPA. CONCLUSIONS The results indicate that BPA decreased the amplitude and frequency of spontaneous uterine contractions by involving the nitrergic mechanism; however, the GC mechanism is not involved in the depression.
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Affiliation(s)
- Hemlata Gupta
- Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Shripad B Deshpande
- Department of Physiology, SRMS-Institute of Medical Sciences, Bareilly-243202, UP, India.,Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi-221005, India, Phone: +91-9450530236, Fax: +91-581-2582030
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S-Nitrosoglutathione Reductase Underlies the Dysfunctional Relaxation to Nitric Oxide in Preterm Labor. Sci Rep 2018; 8:5614. [PMID: 29618799 PMCID: PMC5884813 DOI: 10.1038/s41598-018-23371-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 03/06/2018] [Indexed: 12/11/2022] Open
Abstract
Tocolytics show limited efficacy to prevent preterm delivery. In uterine smooth muscle cGMP accumulation following addition of nitric oxide (NO) has little effect on relaxation suggesting a role for protein S-nitrosation. In human myometrial tissues from women in labor at term (TL), or spontaneously in labor preterm (sPTL), direct stimulation of soluble guanylyl cyclase (sGC) fails to relax myometrium, while the same treatment relaxes vascular smooth muscle completely. Unlike term myometrium, effects of NO are not only blunted in sPTL, but global protein S-nitrosation is also diminished, suggesting a dysfunctional response to NO-mediated protein S-nitrosation. Examination of the enzymatic regulator of endogenous S-nitrosoglutathione availability, S-nitrosoglutathione reductase, reveals increased expression of the reductase in preterm myometrium associated with decreased total protein S-nitrosation. Blockade of S-nitrosoglutathione reductase relaxes sPTL tissue. Addition of NO donor to the actin motility assay attenuates force. Failure of sGC activation to mediate relaxation in sPTL tissues, together with the ability of NO to relax TL, but not sPTL myometrium, suggests a unique pathway for NO-mediated relaxation in myometrium. Our results suggest that examining the action of S-nitrosation on critical contraction associated proteins central to the regulation of uterine smooth muscle contraction can reveal new tocolytic targets.
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Ulrich C, Quilici DR, Schlauch KA, Buxton ILO. The human uterine smooth muscle S-nitrosoproteome fingerprint in pregnancy, labor, and preterm labor. Am J Physiol Cell Physiol 2013; 305:C803-16. [PMID: 23948706 DOI: 10.1152/ajpcell.00198.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Molecular mechanisms involved in uterine quiescence during gestation and those responsible for induction of labor at term are incompletely known. More than 10% of babies born worldwide are premature and 1,000,000 die annually. Preterm labor results in preterm delivery in 50% of cases in the United States explaining 75% of fetal morbidity and mortality. There is no Food and Drug Administration-approved treatment to prevent preterm delivery. Nitric oxide-mediated relaxation of human uterine smooth muscle is independent of global elevation of cGMP following activation of soluble guanylyl cyclase. S-nitrosation is a likely mechanism to explain cGMP-independent relaxation to nitric oxide and may reveal S-nitrosated proteins as new therapeutic targets for the treatment of preterm labor. Employing S-nitrosoglutathione as an nitric oxide donor, we identified 110 proteins that are S-nitrosated in 1 or more states of human pregnancy. Using area under the curve of extracted ion chromatograms as well as normalized spectral counts to quantify relative expression levels for 62 of these proteins, we show that 26 proteins demonstrate statistically significant S-nitrosation differences in myometrium from spontaneously laboring preterm patients compared with nonlaboring patients. We identified proteins that were up-S-nitrosated as well as proteins that were down-S-nitrosated in preterm laboring tissues. Identification and relative quantification of the S-nitrosoproteome provide a fingerprint of proteins that can form the basis of hypothesis-directed efforts to understand the regulation of uterine contraction-relaxation and the development of new treatment for preterm labor.
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Affiliation(s)
- Craig Ulrich
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada; and
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Ulrich C, Quillici DR, Schegg K, Woolsey R, Nordmeier A, Buxton ILO. Uterine smooth muscle S-nitrosylproteome in pregnancy. Mol Pharmacol 2011; 81:143-53. [PMID: 22027755 DOI: 10.1124/mol.111.075804] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The molecular mechanisms involved in uterine quiescence during gestation and those responsible for induction of labor are not completely known. Nitric oxide relaxes uterine smooth muscle in a manner disparate from that for other smooth muscles because global elevation of cGMP after activation of soluble guanylyl cyclase does not relax the muscle. S-Nitrosylation, the covalent addition of an nitric oxide (NO) group to a cysteine thiol is a likely mechanism to explain the ability of NO to relax myometrium. This work is the first to describe the myometrial S-nitrosylproteome in both pregnant and nonpregnant tissue states. Using the guinea pig model, we show that specific sets of proteins involved in contraction and relaxation are S-nitrosylated in laboring and nonlaboring muscle and that many of these proteins are uniquely S-nitrosylated in only one state of the tissue. In particular, we show that S-nitrosylation of the intermediate filament protein desmin is significantly increased (5.7-fold, p < 0.005) in pregnancy and that this increase cannot be attributed solely to the increase in protein expression (1.8-fold, p < 0.005) that accompanies pregnancy. Elucidation of the myometrial S-nitrosylproteome provides a list of mechanistically important proteins that can constitute the basis of hypotheses formed to explain the regulation of uterine contraction/relaxation.
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Affiliation(s)
- Craig Ulrich
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557, USA
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Rizzo A, Trisolini C, Spedicato M, Mutinati M, Minoia G, Sciorsci RL. In vitro effects of L-arginine on spontaneous and Homocysteine-induced contractility of pregnant canine uteri. Theriogenology 2011; 76:715-20. [DOI: 10.1016/j.theriogenology.2011.04.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 03/28/2011] [Accepted: 04/03/2011] [Indexed: 10/18/2022]
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A role of stretch-activated potassium currents in the regulation of uterine smooth muscle contraction. Acta Pharmacol Sin 2011; 32:758-64. [PMID: 21642947 DOI: 10.1038/aps.2011.62] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Rates of premature birth are alarming and threaten societies and healthcare systems worldwide. Premature labor results in premature birth in over 50% of cases. Preterm birth accounts for three-quarters of infant morbidity and mortality. Children that survive birth before 34 weeks gestation often face life-long disability. Current treatments for preterm labor are wanting. No treatment has been found to be generally effective and none are systematically evaluated beyond 48 h. New approaches to the treatment of preterm labor are desperately needed. Recent studies from our laboratory suggest that the uterine muscle is a unique compartment with regulation of uterine relaxation unlike that of other smooth muscles. Here we discuss recent evidence that the mechanically activated 2-pore potassium channel, TREK-1, may contribute to contraction-relaxation signaling in uterine smooth muscle and that TREK-1 gene variants associated with human labor and preterm labor may lead to a better understanding of preterm labor and its possible prevention.
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Chiossi G, Costantine MM, Betancourt A, Hankins GD, Longo M, Saade GR, Bytautiene E. Does sildenafil citrate affect myometrial contractile response to nifedipine in vitro? Am J Obstet Gynecol 2010; 203:252.e1-5. [PMID: 20541728 DOI: 10.1016/j.ajog.2010.05.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 04/09/2010] [Accepted: 05/05/2010] [Indexed: 11/26/2022]
Abstract
OBJECTIVE We sought to test the hypothesis that sildenafil citrate (SC) at low concentrations potentiates the tocolytic effects of nifedipine in vitro. STUDY DESIGN Myometrial biopsies were obtained from 22 term nonlaboring women undergoing scheduled cesarean delivery. Tissue strips were suspended in organ chambers for isometric tension recording, and incubated for 30 minutes with either SC at 231 ng/mL or solvent. The effects of cumulative doses (10(-10) to 10(-5) mol/L) of nifedipine on spontaneous and oxytocin-induced uterine contractility were then determined. Areas under the contraction curve were compared using 1-way analysis of variance with Tukey post hoc test (significance: P < .05). RESULTS Nifedipine significantly inhibited spontaneous and oxytocin-induced myometrial contractility. Preincubation with SC increased response to nifedipine and significantly potentiated its inhibitory effect at 10(-8) mol/L, without affecting oxytocin-induced contractile response. CONCLUSION At concentrations within a therapeutic window, SC increases myometrial sensitivity to nifedipine.
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Buxton ILO, Singer CA, Tichenor JN. Expression of stretch-activated two-pore potassium channels in human myometrium in pregnancy and labor. PLoS One 2010; 5:e12372. [PMID: 20811500 PMCID: PMC2928262 DOI: 10.1371/journal.pone.0012372] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Accepted: 07/30/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND We tested the hypothesis that the stretch-activated, four-transmembrane domain, two pore potassium channels (K2P), TREK-1 and TRAAK are gestationally-regulated in human myometrium and contribute to uterine relaxation during pregnancy until labor. METHODOLOGY We determined the gene and protein expression of K2P channels in non-pregnant, pregnant term and preterm laboring myometrium. We employed both molecular biological and functional studies of K2P channels in myometrial samples taken from women undergoing cesarean delivery of a fetus. PRINCIPAL FINDINGS TREK-1, but not TREK-2, channels are expressed in human myometrium and significantly up-regulated during pregnancy. Down-regulation of TREK-1 message was seen by Q-PCR in laboring tissues consistent with a role for TREK-1 in maintaining uterine quiescence prior to labor. The TRAAK channel was unregulated in the same women. Blockade of stretch-activated channels with a channel non-specific tarantula toxin (GsMTx-4) or the more specific TREK-1 antagonist L-methionine ethyl ester altered contractile frequency in a dose-dependent manner in pregnant myometrium. Arachidonic acid treatment lowered contractile tension an effect blocked by fluphenazine. Functional studies are consistent with a role for TREK-1 in uterine quiescence. CONCLUSIONS We provide evidence supporting a role for TREK-1 in contributing to uterine quiescence during gestation and hypothesize that dysregulation of this mechanism may underlie certain cases of spontaneous pre-term birth.
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Affiliation(s)
- Iain L O Buxton
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Nevada, United States of America.
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Buxton ILO, Milton D, Barnett SD, Tichenor SD. Agonist-specific compartmentation of cGMP action in myometrium. J Pharmacol Exp Ther 2010; 335:256-63. [PMID: 20651027 DOI: 10.1124/jpet.110.171934] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nitric oxide relaxes myometrium in a cGMP-independent manner. Although cGMP activates its cognate kinase, this is not required for the inhibitory effect of nitric oxide. Thus, nitric oxide-mediated cGMP elevation does not enjoy the same set of substrates as it does in other smooth muscles. To further understand the regulation of relaxation of uterine muscle by cGMP, we have studied the actions of peptide-mediated cGMP action in guinea pig myometrium. We used both functional and biochemical studies of the action of the particulate guanylyl cyclase activator uroguanylin and its receptor, particulate guanylyl cyclase type C, to address the relationship between cGMP elevation acting in the membrane signaling domain to that of the nonmembrane region of the cell. Uroguanylin relaxed oxytocin-induced contractions in a dose-dependent fashion only in pregnant myometrium. Both relaxation and cGMP accumulation after uroguanylin stimulation were blocked by the putative particulate guanylyl cyclase type C inhibitors 2-chloro-ATP and isatin (1H-indole-2,3-dione), but not by the soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-A]quinoxalin-1-one (ODQ). Uroguanylin stimulated cGMP accumulation only in the pregnant myometrium. Caveolin-1 expression increased in pregnancy toward term. In the caveolin-1-containing membrane domain, uroguanylin, but not the nitric-oxide donor, led to the elevation of cGMP that was insensitive to ODQ. Particulate guanylyl cyclase C was expressed and prouroguanylin was detected in pregnant myometrium. We conclude that a uroguanylin-particulate cyclase-cGMP relaxation pathway is present and cGMP is compartmented in myometrium. The agonist-mediated selectivity of relaxation to cGMP is of fundamental pharmacological interest in understanding signal transduction in smooth muscle.
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Affiliation(s)
- Iain L O Buxton
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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Perez-Rojas JM, Kassem KM, Beierwaltes WH, Garvin JL, Herrera M. Nitric oxide produced by endothelial nitric oxide synthase promotes diuresis. Am J Physiol Regul Integr Comp Physiol 2010; 298:R1050-5. [PMID: 20147612 DOI: 10.1152/ajpregu.00181.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Extracellular fluid volume is highly regulated, at least in part, by peripheral resistance and renal function. Nitric oxide (NO) produced by NO synthase type 3 (NOS 3) in the nonrenal vasculature may promote fluid retention by reducing systemic vascular resistance and arterial pressure. In contrast, NO produced by renal NOS 3 promotes water excretion by reducing renal vascular resistance, increasing glomerular filtration, and inhibiting reabsorption along the nephron. Thus, the net effect of NO from NOS 3 on urinary volume (UV) is unclear. We hypothesized that NO produced by NOS 3 promotes water excretion primarily due to renal tubular effects. We gave conscious wild-type and NOS 3 -/- mice an acute volume load and measured UV, blood pressure, plasma renin concentration (PRC), Na(+), vasopressin, and urinary Na(+) and creatinine concentrations. To give the acute volume load, we trained mice to drink a large volume of water while in metabolic cages. On the day of the experiment, water was replaced with 1% sucrose, and mice had access to it for 1 h. Volume intake was similar in both groups. Over 3 h, wild-type mice excreted 62 +/- 10% of the volume load, but NOS 3 -/- excreted only 42 +/- 5% (P < 0.05). Blood pressure in NOS 3 -/- was 118 +/- 3 compared with 110 +/- 2 mmHg in wild-type mice (P < 0.05), but it did not change following volume load in either strain. PRC, vasopressin, and glomerular filtration rate were similar between groups. Urinary Na(+) excretion was 49.3 +/- 7.0 in wild-type vs. 37.8 +/- 6.4 mumol/3 h in NOS 3 -/- mice (P < 0.05). Bumetanide administration eliminated the difference in volume excretion between wild-type and NOS 3 -/- mice. We conclude that 1) NO produced by NOS 3 promotes water and Na(+) excretion and 2) the renal epithelial actions of NO produced by NOS 3 supersede the systemic and renal vascular actions.
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Affiliation(s)
- Jazmin M Perez-Rojas
- Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI 48202, USA
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Buxton ILO. Nitric oxide stimulation of cGMP accumulation in myometrial cells from pregnant women is antagonized by oxytocin. PROCEEDINGS OF THE WESTERN PHARMACOLOGY SOCIETY 2008; 51:78-82. [PMID: 19544684 PMCID: PMC2702707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The role of cGMP in the myometrium of pregnant women is not completely known. We have previously shown in guinea pig, monkey and man that NO-induced relaxation of oxytocin-induced contractions is independent of cGMP accumulation. To approach an understanding of the role of cGMP in myometrium, we have developed smooth muscle cell cultures from pregnant women undergoing caesarian section at term. Cells, grown in standard media containing progesterone, express smooth muscle cell markers and are used within five doublings. Cells stimulated with NO donors increase their cGMP levels nearly 100 fold (basal = approximately 9 pmol/mg protein). In the presence of oxytocin (OT; 1 microM), cGMP accumulation in the presence of NO (100 microM) is significantly blunted (25 fold). Cyclic GMP-degradation is inhibited by the presence of the phosphodiesterase inhibitor zaprinast; suggesting that the ability of OT to attenuate cGMP accumulation is unlikely to be due to degradation. We propose that the elevation of intracellular calcium following the addition of OT suppress the activity of a calcium-sensitive guanylyl cyclase. The diminution of cGMP synthetic potential in myometrial cells from pregnant women is consistent with the absence of a role for cGMP in the NO-induced relaxation of uterine muscle.
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Affiliation(s)
- Iain L O Buxton
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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Bulbul A, Yağci A, Altunbaş K, Sevimli A, Celik HA, Karadeniz A, Akdağ E. The role of nitric oxide in the effects of ovarian steroids on spontaneous myometrial contractility in rats. Theriogenology 2007; 68:1156-68. [PMID: 17869333 DOI: 10.1016/j.theriogenology.2007.08.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 07/26/2007] [Accepted: 08/02/2007] [Indexed: 10/22/2022]
Abstract
Forty ovariectomized rats were apportioned into one control and three experimental groups (n=10 each) to evaluate the role of nitric oxide in the effects of ovarian steroids on spontaneous myometrial contractility in rats. The control group (group Ov) received sesame oil once daily for 10 days, whereas rats in the experimental groups were treated with progesterone (2 mg/(rat day); group P), 17beta-estradiol (10 microg/(rat day); group E2), or progesterone and 17beta-estradiol together (group E2+P). The functionality of the arginine-nitric oxide synthase (NOS)-nitric oxide (NO) pathway in the uterine horns of sacrificed rats was evaluated in an isolated organ bath. L-Arginine, sodium nitroprusside (SNP) and 8-Br-cGMP decreased uterine contractile tension induced by electric field stimulation (EFS) in the Ov, P, and E2+P groups, but not in the E2 group. In addition, L-arginine was ineffective when applied together with a NOS inhibitor, L-nitro-N-arginine (L-NNA). The percentage of contractile inhibition was higher in the Ov and P groups compared to the E2+P group. Immunohistochemical evaluation revealed that expression of neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS) in smooth muscles and nerve cells did not differ among the groups. Expression of nNOS and eNOS was strongly evident in the E2 and E2+P groups at both surface and glandular epithelium of the endometrium. iNOS expression was increased in surface epithelium of the E2 and E2+P groups. However, iNOS expression was only increased in glandular epithelial cells of the E2+P group. In conclusion, the L-arginine-NOS-NO pathway inhibits myometrial contractions via cGMP-dependent and -independent mechanisms, and while progesterone maintains the nitric oxide effects, estrogen prevents them. These results suggest that NOS does not mediate the effects of estrogen.
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Affiliation(s)
- A Bulbul
- Department of Physiology, Faculty of Veterinary Medicine, Afyon Kocatepe University, Afyon, Turkey.
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De Man JG, De Winter BY, Herman AG, Pelckmans PA. Study on the cyclic GMP-dependency of relaxations to endogenous and exogenous nitric oxide in the mouse gastrointestinal tract. Br J Pharmacol 2006; 150:88-96. [PMID: 17115067 PMCID: PMC2013844 DOI: 10.1038/sj.bjp.0706964] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND AND PURPOSE cGMP mediates nitrergic relaxations of intestinal smooth muscle, but several studies have indicated that cGMP-independent mechanisms may also be involved. We addressed this contention by studying the effect of ODQ and ns2028, specific inhibitors of soluble guanylate cyclase, on nitrergic relaxations of the mouse gut. EXPERIMENTAL APPROACH Mouse gastric fundus and small intestinal muscle preparations were mounted in organ baths to study relaxations to exogenous NO, NO donors and electrical field stimulation (EFS) of enteric nerves. KEY RESULTS In gastric fundus longitudinal muscle strips, ODQ and NS2028 abolished the L-nitroarginine-sensitive relaxations to EFS and the relaxations to NO and NO donors, glyceryl trinitrate (GTN), SIN-1 and sodium nitroprusside (SNP). EFS of intestinal segments and muscle strips showed L-nitroarginine-resistant relaxations, which were abolished by the purinoceptor blocker suramin. In the presence of suramin, ODQ and NS2028 abolished all relaxations to EFS in intestinal segments and strips. ODQ and NS2028 abolished the relaxations to exogenous NO and to the NO donors GTN, SIN-1 and SNP in circular and longitudinal intestinal muscle strips. Intestinal segments showed residual relaxations to NO and GTN. CONCLUSIONS AND IMPLICATIONS Our results indicate that relaxations to endogenous NO in the mouse gastric fundus and small intestine are completely dependent on cGMP. ODQ and NS2028 incompletely blocked nitrergic relaxations to exogenous NO in intact intestinal segments. However, it is unlikely that this is due to the involvement of cGMP-independent pathways because ODQ and NS2028 abolished all relaxations to endogenous and exogenous NO in intestinal muscle strips.
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Affiliation(s)
- J G De Man
- Division of Gastroenterology, Faculty of Medicine, University of Antwerp, Antwerp, Belgium.
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Demirkoprulu N, Cetin M, Bagcivan I, Kaya T, Soydan AS, Karadas B, Cetin A. Comparative relaxant effects of YC-1 and DETA/NO on spontaneous contractions and the levels of cGMP of isolated pregnant rat myometrium. Eur J Pharmacol 2005; 517:240-5. [PMID: 15985262 DOI: 10.1016/j.ejphar.2005.05.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2005] [Revised: 05/12/2005] [Accepted: 05/24/2005] [Indexed: 10/25/2022]
Abstract
This study was designed to compare the effects of YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole), a nitric oxide (NO)-independent soluble guanylate cyclase activator, and diethylenetriamine-NONOate (DETA/NO), a NO donor, on spontaneous contractions and the levels of cyclic GMP (cGMP) of myometrial strips isolated from timed-pregnant rats. Myometrial strips were obtained from timed-pregnant Wistar albino rats (n=10) and were mounted in organ baths and tested for changes in isometric tension in response to YC-1 and DETA/NO. We also evaluated the effect of YC-1 and DETA/NO on the levels of cGMP in myometrial strips obtained from timed-pregnant rat uterine horns (n=20). YC-1 (10(-9)-3x10(-5) M) and DETA/NO (10(-7)-10(-4) M) concentration-dependently decreased the amplitude and frequency of spontaneous contractions of myometrial strips isolated from term-pregnant rats. The inhibitions of the amplitude and frequency of spontaneous contractions by YC-1 and DETA/NO were antagonized with methylene-blue (10(-5) M). Antagonistic effect of methylene-blue (10(-5) M) was more on DETA/NO responses than that of YC-1 (P<0.05). In addition, YC-1-stimulated myometrial strips showed more elevation in myometrial cGMP than that of DETA/NO (P<0.05). We demonstrated that YC-1 and DETA/NO induce relaxations in the amplitude and frequency of spontaneous contractions of myometrial strips with different potencies. We also found that YC-1 and DETA/NO-induced relaxations are associated with significant increases in cGMP. These results might suggest that the relaxant effects of YC-1 and DETA/NO on the rat myometrium could be due to the stimulation of the soluble guanylate cyclase and cGMP may play a role for the maintenance of uterine quiescence during pregnancy.
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Affiliation(s)
- Nihal Demirkoprulu
- Department of Obstetrics and Gynecology, Cumhuriyet University School of Medicine, 58140, Sivas, Turkey
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Buxton ILO. Regulation of uterine function: a biochemical conundrum in the regulation of smooth muscle relaxation. Mol Pharmacol 2004; 65:1051-9. [PMID: 15102932 DOI: 10.1124/mol.65.5.1051] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Premature birth accounts for the majority of fetal morbidity and mortality in the developed world and is disproportionately represented in some populations, such as African Americans in the United States. The costs associated with prematurity are staggering in both monetary and human terms. Present therapeutic approaches for the treatment of labor leading to preterm delivery are inadequate and our understanding of the regulation of myometrial smooth muscle contraction-relaxation is incomplete. The ability of nitric oxide to relax smooth muscle has led to an interest in employing nitric oxide-donors in the treatment of preterm labor. Fundamental differences exist, however, in the regulation of uterine smooth muscle relaxation and that of other smooth muscles and constitute a conundrum in our understanding. We review the evidence that nitric oxide-mediated relaxation of myometrial smooth muscle, unlike vascular or gastrointestinal smooth muscle, is independent of global elevation of cyclic guanosine 5'-monophosphate. Applying our current understanding of microdomain signaling and taking clues from genomic studies of pregnancy, we offer a framework in which to view the apparent conundrum and suggest testable hypotheses of uterine relaxation signaling that can explain the mechanistic distinctions. We propose that understanding these mechanistic distinctions in myometrium will reveal molecular targets that are unique and thus may be explored as therapeutic targets in the development of new uterine smooth muscle-specific tocolytics.
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Affiliation(s)
- Iain L O Buxton
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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Cetin A, Kaya T, Demirkoprulu N, Karadas B, Duran B, Cetin M. YC-1, a Nitric Oxide-Independent Activator of Soluble Guanylate Cyclase, Inhibits the Spontaneous Contractions of Isolated Pregnant Rat Myometrium. J Pharmacol Sci 2004; 94:19-24. [PMID: 14745113 DOI: 10.1254/jphs.94.19] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The aim of this study was to investigate the effect of YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole) on spontaneous contractions and levels of cyclic GMP (cGMP) of myometrial strips isolated from pregnant rats. It is a nitric oxide-independent soluble guanylate cyclase activator. Myometrial strips were obtained from eight pregnant Wistar albino rats and were mounted in organ baths for the recording of isometric tensions. We evaluated the effect of increasing concentrations of YC-1 on spontaneous myometrial contractions and on contractions of myometrial smooth muscle pretreated with methylene blue (10(-5) M), tetraethylammonium chloride (TEA) (3 x 10(-4) M), and glibenclamide (10(-6) M). YC-1 (10(-9) - 3 x 10(-5) M) concentration-dependently decreased the amplitude and frequency of spontaneous contractions of myometrial strips. The inhibition of the amplitude and frequency of spontaneous contractions by YC-1 were antagonized with methylene blue (10(-5) M) and TEA (3 x 10(-4) M), but they were not changed by glibenclamide (10(-6) M); however, the antagonistic effect of methylene blue was significantly more than that of TEA (P<0.05). We also evaluated the effect of YC-1 on the levels of cGMP in myometrial strips obtained from pregnant rat uterine horns. YC-1-stimulated myometrial strips showed an excessive elevation in myometrial cGMP that declined slowly during the subsequent washout period. These results show that YC-1 decreases spontaneous contractile activity of myometrial strips isolated from pregnant rat and causes elevation of myometrial cGMP levels in vivo. This effect of YC-1 is significantly reduced by the methylene blue and TEA, suggesting the activation of soluble guanylate cyclase and Ca(2+)-sensitive K(+) channels as the mechanisms of action.
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Affiliation(s)
- Ali Cetin
- Department of Obstetrics and Gynecology, Cumhuriyet University School of Medicine, Sivas, Turkey.
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20
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Tichenor SD, Malmquist NA, Buxton ILO. Dissociation of cGMP accumulation and relaxation in myometrial smooth muscle: effects of S-nitroso-N-acetylpenicillamine and 3-morpholinosyndonimine. Cell Signal 2003; 15:763-72. [PMID: 12781869 DOI: 10.1016/s0898-6568(03)00006-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In guinea pig, primate and man, nitric oxide (NO)-induced regulation of myometrial smooth muscle contraction is distinct from other smooth muscles because cyclic guanosine 3',5'-cyclic monophosphate (cGMP) accumulation is neither necessary nor sufficient to relax the tissue. To further our understanding of the mechanism of action of NO in myometrium, we employed the NO donors, S-nitroso-N-acetylpenicillamine (SNAP), and 3-morpholinosyndonimine (SIN-1) proposed to relax airway smooth muscle by disparate mechanisms involving elevation in intracellular calcium ([Ca(2+)](i)) or cGMP accumulation, respectively. Treatment of guinea pig myometrial smooth muscle with either NO donor at concentrations thought to produce maximal relaxation of smooth muscles resulted in significant elevations in cGMP that were accompanied by phosphorylation of the cGMP-dependent protein kinase substrate vasodilator-stimulated phosphoprotein (VASP), shown here for the first time to be present and phosphorylated in myometrium. Stimulation of myometrial strips with oxytocin (OT, 1 microM) produced an immediate increase in contractile force that persisted in the continued presence of the agonist. Addition of SNAP (100 microM) in the presence of OT relaxed the tissue completely as might be expected of an NO donor. SIN-1 failed to relax the myometrium at any concentration tested up to 300 microM. In Fura-2 loaded myometrial cells prepared from guinea pig, addition of SNAP (100 microM) in the absence of other agonists caused a significant, reproducible elevation of intracellular calcium while SIN-1 employed under the same conditions did not. Our data further support the notion that NO action in myometrium is distinct from that in other smooth muscles and underscores the possibility that discrete regional changes in [Ca(2+)](i), rather than cGMP, signal NO-induced relaxation of the muscle.
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Affiliation(s)
- Stephen D Tichenor
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557-0270, USA
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Kim T, La J, Lee J, Yang I. Effects of nitric oxide on slow waves and spontaneous contraction of guinea pig gastric antral circular muscle. J Pharmacol Sci 2003; 92:337-47. [PMID: 12939518 DOI: 10.1254/jphs.92.337] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
We examined the effects of nitric oxide (NO) donors, S-nitroso-L-cysteine (Cys-NO) and 3-morpholinosydnonimine hydrochloride (SIN-1), on slow waves and contractile activity in the circular muscle of guinea pig gastric antrum. In the presence of atropine and guanethidine, electrical field stimulation (EFS) reduced the amplitude of phasic contraction. The effect of EFS was significantly inhibited by both the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester and a soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). Cys-NO and SIN-1 mimicked the effect of EFS on phasic contraction and reduced the amplitude of slow waves in a concentration-dependent manner, with no effect on frequency and resting membrane potential. Phasic contraction was more sensitive to NO donors than slow waves. The inhibitory effects of NO donors were antagonized by ODQ and mimicked by a membrane permeable cGMP analogue 8-bromo-cGMP. Several K(+) channel blockers such as apamin, iberiotoxin, and glibenclamide had no effect on the inhibitory action of SIN-1. These results suggest that NO inhibits the phasic contraction and slow waves through cGMP-dependent mechanisms in guinea pig gastric antrum. The effect of NO is unlikely to be mediated by the activation of Ca(2+)-activated or ATP-sensitive K(+) channels.
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Affiliation(s)
- Taewan Kim
- Department of Veterinary Physiology, College of Veterinary Medicine, Seoul National University, Republic of Korea
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Hoffmann P, Stanke-Labesque F, Fanchin R, Dilaï N, Pons JC, Ayoubi JM. Effects of L-arginine and sodium nitroprusside on the spontaneous contractility of human non-pregnant uterus. Hum Reprod 2003; 18:148-51. [PMID: 12525457 DOI: 10.1093/humrep/deg025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The aim of this study was to investigate, in isolated human non-gravid myometrium, the involvement of the cyclic guanosine monophosphate (cGMP) pathway in nitric oxide (NO) induced relaxation. METHODS Strips of human myometrium from hysterectomized women were suspended in organ baths for recording of isometric tension. Cumulative concentration-response curves for L-arginine and sodium nitroprusside were performed in the presence of methylene blue (10 micromol/l) or vehicle (control). The effect of increasing concentrations of 8-bromo-cGMP on uterine spontaneous contraction was also studied. RESULTS L-arginine and sodium nitroprusside induced a concentration-dependent decrease in the amplitude of the myometrial spontaneous contractions. Pre-treatment with methylene blue enhanced the inhibitory effect of L-arginine and sodium nitroprusside on myometrial spontaneous contractions. In addition, 8-bromo-cGMP had no effect on spontaneous contractions in human myometrium. CONCLUSIONS These data provide evidence that L-arginine and sodium nitroprusside inhibit the spontaneous contractions of the non-pregnant human uterus through a cGMP independent pathway.
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Affiliation(s)
- P Hoffmann
- Department of Obstetrics and Gynaecology and Laboratory of Pharmacology, Grenoble University Hospital, Grenoble, BP219, 38043 Grenoble, Cedex 9, France.
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Okawa T, Sato A, Syal AS, Vedernikov YP, Saade GR, Garfield RE. EFFECTS OF NITRIC OXIDE DONORS ON NON-PREGNANT AND PREGNANT RAT UTERINE AND AORTIC SMOOTH MUSCLE. Fukushima J Med Sci 2003; 49:23-32. [PMID: 14603949 DOI: 10.5387/fms.49.23] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVE To compare the effects of nitric oxide (NO) donors, diethylamine/nitric oxide (DEA/NO) and nitroglycerin (NTG), on isolated uterine and aortic tissues from non-pregnant, mid and late pregnant rats. METHODS The uterus and thoracic aorta were obtained from non-pregnant (estrous cycle) and pregnant Sprague-Dawley rats on day 14 and day 21. The uterine and aortic rings were incubated in organ chambers filled with Krebs-Henseleit solution bubbled with 5% CO2 in air for isometric tension recordings. Cumulative concentration-response relationships to DEA/NO and NTG were obtained in the aortic rings contracted with phenylephrine and in spontaneously contracting uterine rings. RESULTS The sensitivity and the maximal inhibitory effects of DEA/NO did not differ in aortic tissues of any group. DEA/NO-induced Maximal inhibition of spontaneous contractions of uterine tissues from mid-pregnant rats was greater (although not significantly) than in the tissues from non-pregnant animals (with similar sensitivity), but it was significantly depressed in tissues from late pregnant rats. The sensitivity to and maximal inhibitory effects of NTG were less in aortic tissues from late pregnant versus mid-pregnant and non-pregnant rats. In uterine tissues from late pregnant rats the effect of NTG was negligible. The inhibitory action of both NO donors was much more pronounced in aortic versus uterine tissues. CONCLUSIONS Uterine smooth muscle is less sensitive than vascular smooth muscle to NO. Uterine smooth muscle from late pregnant animals demonstrates refractoriness to both DEA/NO and NTG, while vascular smooth muscle from late pregnant animals demonstrates refractoriness to NTG, but not to DEA/NO.
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Affiliation(s)
- Toshiaki Okawa
- Department of Obstetrics, Fukushima Medical University School of Medicine, Fukushima, Japan
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Agha AM, Taha RA. Sildenafil inhibits agonist-evoked rat uterine contractility: influence of guanylyl cyclase inhibition. Eur J Pharmacol 2001; 428:343-8. [PMID: 11689193 DOI: 10.1016/s0014-2999(01)01351-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Sildenafil shows a potent relaxant effect on corpus cavernosum smooth muscles by prolonging cyclic guanosine monophosphate (cGMP) actions. We investigated whether this inhibitory effect of sildenafil was also displayed on the uterine musculature. Isolated uteri of non-pregnant rats were used to measure the possible sildenafil-induced inhibition of contractions evoked by various oxytocic agents, viz., prostaglandin E2, oxytocin and acetylcholine. The relation of these effects to sildenafil action on cGMP was also examined, using methylene blue as a guanylyl cyclase inhibitor. Sildenafil (30 and 100 nM) was found to shift to the right the non-cumulative concentration-response curves of the test agonists in a concentration-dependent manner. The shift was accompanied by a reduction in the maximal response of the tissue to all uterine stimulants selected. Sildenafil also elicited a marked concentration-dependent increase in EC25 of prostaglandin E2, oxytocin and acetylcholine, as compared to their respective control values. Preincubation of the uterine strip with methylene blue (10 microM) reduced the inhibitory effects of sildenafil on oxytocin- and acetylcholine-evoked contractions, at submaximal concentrations of each agonist. The results suggest that sildenafil inhibits the uterotonic potentials of various oxytocic agents and that this effect could be probably related to the drug's action on cGMP.
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Affiliation(s)
- A M Agha
- Department of Pharmacology, Faculty of Pharmacy, Cairo University, Kasr El-Aini Street, 11562, Cairo, Egypt.
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25
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Buxton IL, Kaiser RA, Malmquist NA, Tichenor S. NO-induced relaxation of labouring and non-labouring human myometrium is not mediated by cyclic GMP. Br J Pharmacol 2001; 134:206-14. [PMID: 11522613 PMCID: PMC1572926 DOI: 10.1038/sj.bjp.0704226] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. In myometrial strips from near-term non-labouring human uterus, addition of oxytocin (OT) evoked dose-dependent (10 - 3000 nM) phasic contractions that were antagonized by atosiban (1 microM) and relaxed by addition of the nitric oxide donor S-nitroso L-cysteine (Cys-NO). In near-term labouring myometrium, however, addition of OT was ineffective at raising additional tone. 2. In both labouring and non-labouring tissue, Cys-NO mediated relaxation of spontaneous or OT-induced contractions (IC(50)=1 microM) was unaffected by prior addition of the guanylyl cyclase (GC) inhibitors ODQ (1H-[1,2,4]oxadiazolo[4,3,-alpha]quinoxalin-1-one; 1 microM), or methylene blue (MB; 10 microM). 3. Elevation of intracellular cyclic GMP accompanying 30 microM Cys-NO addition in non-labouring tissue (7.5 fold) or in labouring tissues (2.5 fold) was completely blocked in tissues that had been pre-treated with ODQ or MB. 4. Charybdotoxin (ChTx), iberiotoxin (IbTx) and kaliotoxin (KalTx) all shifted the Cys-NO inhibition curve to the right and reduced the degree of relaxation produced by maximal Cys-NO treatment (100 microM in non-labouring tissue; in labouring tissue, KalTx prevented Cys-NO mediated relaxation in both stimulated and unstimulated tissue. 5. Addition of the NO-donor S-nitroso N-acetyl penicillamine (SNAP) produced a dose-dependent relaxation of pregnant myometrium while 3-morpholinosyndonimine (SIN-1) did not. The failure of SIN-1 to relax OT-induced contractions was not due to a failure of the donor to stimulate myometrial GC. 6. We demonstrate that despite the ability of NO to stimulate myometrial GC in pregnant uterine muscle, relaxations are independent of cyclic GMP action. Effects of K(+)-channel inhibitors suggests that NO-induced relaxation in human uterine smooth muscle may be subserved by direct or indirect activation of one or more calcium-activated K(+)-channels.
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Affiliation(s)
- I L Buxton
- Department of Pharmacology, MS318, University of Nevada School of Medicine, Reno, NV 89557, USA.
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26
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Fulep E, Vedernikov Y, Saade GR, Garfield RE. Contractility of late pregnant rat myometrium is refractory to activation of soluble but not particulate guanylate cyclase. Am J Obstet Gynecol 2001; 185:158-62. [PMID: 11483921 DOI: 10.1067/mob.2001.114871] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE Our purpose was to compare the effects of agents activating particulate or soluble guanylate cyclases on the spontaneous contractile activity of the isolated pregnant rat uterus. STUDY DESIGN Uterine rings from midpregnant (14-day) and late pregnant (21-day) rats were suspended in organ chambers to record spontaneous contractile activity. Concentration-response curves were obtained for the following natriuretic peptides: atrial, brain, and C-type; concentration-response curves were also obtained for diethylamine nitric oxide, 3-morpholino-sydnominine, and authentic nitric oxide. RESULTS All 3 natriuretic peptides inhibited spontaneous uterine contractions equally at midgestation and late gestation. The inhibitory effects of the nitric oxide donors diethylamine nitric oxide, 3-morpholino-sydnominine, and authentic nitric oxide were attenuated in uterine tissues from animals in late stages of pregnancy. CONCLUSION Agents activating either soluble or particulate guanylate cyclase inhibit contractions of uterine rings from midgestation rats, whereas the effects of soluble guanylate cyclase are attenuated at late pregnancy. Thus spontaneous uterine contractions are under the control of both soluble and particulate guanylate cyclases; the former is dependent on gestational age but the latter is not.
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Affiliation(s)
- E Fulep
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555, USA
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Cornwell TL, Li J, Sellak H, de Lanerolle P, Rodgers WH, Miller RT, Word RA. Regulation of cyclic guanosine monophosphate-dependent protein kinase in human uterine tissues during the menstrual cycle. Biol Reprod 2001; 64:857-64. [PMID: 11207201 DOI: 10.1095/biolreprod64.3.857] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Contractility of uterine smooth muscle is essential for the cyclic shedding of the endometrial lining and also for expulsion of the fetus during parturition. The nitric oxide (NO)-cGMP signaling pathway is involved in smooth muscle relaxation. The downstream target of this pathway essential for decreasing cytoplasmic calcium and muscle tone is the cGMP-dependent protein kinase (PKG). The present study was undertaken to localize expression of PKG in tissues of the female reproductive tract and to test the hypothesis that uterine smooth muscle PKG levels vary with the human menstrual cycle. Immunohistochemistry was used to localize PKG in myometrium, cervix, and endometrium obtained during proliferative and secretory phases. The PKG was localized to uterine and vascular smooth muscle cells in myometrium, stromal cells in endometrium, and a small percentage of cervical stromal cells. Using Western blot analysis and protein kinase activity assays, the expression of PKG was reduced significantly in progesterone-dominated uteri compared with myometrium from postmenopausal women or women in the proliferative phase. These findings support a role for PKG in the control of uterine and vascular smooth muscle contractility during the menstrual cycle.
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Affiliation(s)
- T L Cornwell
- Department of Pathology, Division of Molecular and Cellular Pathology, University of Alabama at Birmingham, Birmingham, Alabama 35294-0019, USA.
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Buhimschi IA, San Martin-Clark O, Aguan K, Thompson LP, Weiner CP. Differential alterations in responsiveness in particulate and soluble guanylate cyclases in pregnant guinea pig myometrium. Am J Obstet Gynecol 2000; 183:1512-9. [PMID: 11120520 DOI: 10.1067/mob.2000.107462] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The mechanism underlying myometrial quiescence during pregnancy is unknown. Our group has previously shown that during pregnancy myometrial cyclic guanosine monophosphate content rises to several hundred times the nonpregnant levels, only to abruptly decline days before the onset of labor. Cyclic guanosine monophosphate plays an integral role in the relaxation of smooth muscle. The aim of this investigation was therefore to determine the effects of pregnancy on both soluble and particulate guanylate cyclase enzymatic activities and messenger ribonucleic acid expressions. STUDY DESIGN Myometrium was obtained from randomly cycling adult nonpregnant guinea pigs and near-term (50-60 days' gestation) pregnant guinea pigs of similar chronologic age. Subcellular fractions were prepared by differential ultracentrifugation. Guanylate cyclase activity was determined by the conversion of guanosine triphosphate to cyclic guanosine monophosphate under basal or stimulated conditions in either the soluble guanylate cyclase or particulate guanylate cyclase fraction. A nitric oxide donor, S-nitroso- N-penacillamine, was used to activate soluble guanylate cyclase (n = 10 animals in each group). Several natriuretic peptides (atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide) and uroguanylin were used to stimulate the different particulate guanylate cyclase isoforms guanylate cyclase A, guanylate cyclase B, and guanylate cyclase C, respectively, in pregnant (n = 8) and nonpregnant (n = 6) animals. Cyclic guanosine monophosphate content was measured by radioimmunoassay, and enzymatic activity was expressed as picomoles of cyclic guanosine monophosphate per milligram of protein per minute. Total guanylate cyclase represented the sum of soluble guanylate cyclase and particulate guanylate cyclase activities for a tissue. To investigate whether the observed changes in guanylate cyclase activity were paralleled by changes in receptor expression, messenger ribonucleic acid levels of the genes for guanylate cyclase A and guanylate cyclase B isoforms were quantified by ribonuclease protection assay (n = 5 animals in each group). RESULTS Under basal conditions particulate guanylate cyclase represented 78% (nonpregnant state) to 88% (during pregnancy) of the total guanylate cyclase activity in the guinea pig myometrium. Pregnancy further reduced myometrial soluble guanylate cyclase (both basal and stimulated by nitric oxide) relative to the nonpregnant state. Pregnancy selectively increased atrial natriuretic peptide-stimulated particulate guanylate cyclase activity (attributed to guanylate cyclase A), although it did not change basal myometrial particulate guanylate cyclase activity in general. Guanylate cyclase B (particulate guanylate cyclase stimulated by C-type natriuretic peptide) and guanylate cyclase C (particulate guanylate cyclase stimulated by uroguanylin) activities were unaltered by pregnancy. The selective increase in responsiveness of particulate guanylate cyclase to atrial natriuretic peptide during pregnancy was not paralleled by an increased in level of messenger ribonucleic acid for the gene for guanylate cyclase A. CONCLUSION Pregnancy reduced the in vitro responsiveness of the myometrial soluble guanylate cyclase to nitric oxide while increasing the responsiveness of the particulate isoform to atrial natriuretic peptide and brain natriuretic peptide through a mechanism independent of any change in receptor expression.
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Affiliation(s)
- I A Buhimschi
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of Maryland School of Medicine, Baltimore 21201-1559, USA
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Abstract
Contraction and relaxation of smooth muscle is a tightly regulated process involving numerous endogenous substances and their intracellular second messengers. We examine the key role of cyclic guanosine monophosphate (cGMP) in mediating smooth muscle relaxation. We briefly review the current art regarding cGMP generation and degradation, while focusing on the recent identification of the molecular mechanisms underlying cGMP-mediated smooth muscle relaxation. cGMP-induced SM relaxation is mediated mainly by cGMP-dependent protein kinase activation. It involves several molecular events culminating in a reduction in intracellular Ca(2+) concentration and a decrease in the sensitivity of the contractile system to Ca(2+). We propose that the cGMP-induced decrease in Ca(2+) sensitivity is a strategic way to achieve "active relaxation" of the smooth muscle. In summary, we present compelling evidence supporting a key role for cGMP as a mediator of smooth muscle relaxation in physiological and pharmacological settings.
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Affiliation(s)
- J A Carvajal
- Department of Obstetrics, Gynecology, and Reproductive Sciences, School of Medicine, University of Maryland-Baltimore, Baltimore, Maryland 21201, USA.
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30
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Mirabile CP, Massmann GA, Figueroa JP. Physiologic role of nitric oxide in the maintenance of uterine quiescence in nonpregnant and pregnant sheep. Am J Obstet Gynecol 2000; 183:191-8. [PMID: 10920330 DOI: 10.1067/mob.2000.105428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE This study evaluated the role of nitric oxide in the maintenance of uterine quiescence in nonpregnant and pregnant ewes. STUDY DESIGN Sixteen ovariectomized nonpregnant and 10 pregnant (115 days' gestation) chronically instrumented ewes were studied. Uterine contractility was assessed by electromyography and intrauterine pressure recordings. Nitric oxide synthase inhibition was induced with nitro-L -arginine methyl ester or aminoguanidine (4. 5 mg/kg per hour) given during estrogen replacement with 17beta-estradiol (100 microg/d) or in late gestation. In the pregnant group we evaluated the ability of nitric oxide synthase inhibition to alter the responsiveness to oxytocin-induced uterine contractility. Blood pressure and common internal iliac artery blood flow were assessed to confirm nitric oxide synthase inhibition. In addition, the effects of the nitric oxide donor nitroglycerin and the cyclooxygenase inhibitor indomethacin were studied in nonpregnant sheep. The effect of nitric oxide in vitro on myometrial spontaneous and induced contractions was also studied. RESULTS In nonpregnant estrogen-replaced sheep, nitric oxide synthase inhibition and nitroglycerin administration did not alter uterine contractility, despite significant changes in blood pressure. In contrast, indomethacin decreased electromyographic results to 70% of baseline after 1 hour and 47% after 2 hours. In pregnant ewes nitric oxide synthase inhibition failed to alter uterine contractility in response to oxytocin. These findings are in contrast to results of the in vitro study in which nitric oxide was shown to relax sheep myometrium. CONCLUSION The absence of significant effects of nitric oxide synthase inhibition and nitric oxide donors on uterine contractility in vivo suggests that nitric oxide does not play a physiologic role in the regulation of uterine contractility in nonpregnant or pregnant ewes.
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Affiliation(s)
- C P Mirabile
- Section on Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1066, USA
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Buxton IL, Crow W, Mathew SO. Regulation of uterine contraction: mechanisms in preterm labor. AACN CLINICAL ISSUES 2000; 11:271-82. [PMID: 11235436 DOI: 10.1097/00044067-200005000-00010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Preterm labor (PTL) is defined as uterine irritability accompanied by cervical dilation and/or effecement that occurs before 37 weeks gestation. In most cases, PTL becomes preterm delivery (PTD), accounting for 8% to 10% of births in the United States. Fetuses born before 37 weeks' gestation are at risk for a multitude of health and developmental problems. Most perinatal morbidity and mortality in the United States are caused by PTL. It is a costly problem, in both monetary and human terms. Although some risk factors have been identified, they by no means identify, in advance, every case of PTL and PTD. Despite the understandable emphasis on attempts to find and test risk factors that predict PTL, the ultimate benefit--preventing PTD--will come only from an understanding of the physiologic mechanisms of parturition and how to halt those processes when they occur too early. This article reviews current approaches to preventing PTD, describes the biology of myometrial contraction, and discusses recent progress from several laboratories including the authors' that may shed light on approaches to inhibit uterine contractility in the setting of PTL.
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Affiliation(s)
- I L Buxton
- Department of Pharmacology, University of Nevada School of Medicine, Howard Research Bldg., Laboratory Suite 216, Reno, NV 89557, USA.
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Modzelewska B, Sipowicz MA, Saavedra JE, Keefer LK, Kostrzewska A. Involvement of K+ATP channels in nitric oxide-induced inhibition of spontaneous contractile activity of the nonpregnant human myometrium. Biochem Biophys Res Commun 1998; 253:653-7. [PMID: 9918782 DOI: 10.1006/bbrc.1998.9844] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nitric oxide (NO), an important endogenous substance, is known to be a strong relaxant of smooth muscle, including myometrium. It has been postulated that the relaxing effect of NO on smooth muscle is achieved by the stimulation of soluble guanylyl cyclase, which leads to an increase in the cyclic guanosine 3',5'-monophosphate (cGMP) levels and hyperpolarization of the cellular membrane. The aim of our study was to investigate the involvement of K+ATP channels in the mechanism of cGMP-independent nitric oxide-induced inhibition of contractile activity of the nonpregnant human myometrium, obtained at hysterectomy. Nitric oxide's influence on contractile activity was recorded in the presence of methylene blue and glybenclamide, blockers of soluble guanylyl cyclase and K+ATP channels, respectively. Nitric oxide, generated by the NO donor DEA/NO, caused a dose-dependent inhibition of the spontaneous contractile activity of human nonpregnant myometrium. Preincubation with methylene blue (5 microM) did not prevent NO-induced relaxation of uterine strips, while 1.5 microM glybenclamide blocked this effect. Our results indicate that nitric oxide relaxes human non-pregnant uterus through K+ATP channels, independent of the cGMP pathway.
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Affiliation(s)
- B Modzelewska
- Department of Biophysics, Medical School, Bialystok, Poland
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Bradley KK, Buxton IL, Barber JE, McGaw T, Bradley ME. Nitric oxide relaxes human myometrium by a cGMP-independent mechanism. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:C1668-73. [PMID: 9843729 DOI: 10.1152/ajpcell.1998.275.6.c1668] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of intracellular guanosine 3',5'-cyclic monophosphate concentration ([cGMP]i) in nitric oxide (NO)-mediated relaxations in the uterus has become controversial. We found the NO donor S-nitroso-L-cysteine (CysNO) to potently (IC50 = 30 nM) inhibit spontaneous contractions in the nonpregnant human myometrium. CysNO treatment increased [cGMP]i significantly (P < 0.001), and this increase was blocked by the guanylyl cyclase inhibitors methylene blue (10 microM) or LY-83583 (1 microM); however, pretreatment with these guanylyl cyclase inhibitors failed to block CysNO-mediated relaxations. Intracellular cAMP concentrations were not altered by treatment of tissues with 10 microM CysNO. Incubation with the cGMP analogs 8-bromo-cGMP or beta-phenyl-1,N2-etheno-cGMP did not significantly affect spontaneous contractility. Pretreatment of tissues with charybdotoxin [a calcium-dependent potassium channel (BK) blocker] completely reversed CysNO-induced relaxations. We conclude that NO is a potent inhibitor of spontaneous contractile activity in the nonpregnant human uterus and that, although guanylyl cyclase and BK activities are increased by NO, increases in [cGMP]i are not required for NO-induced relaxations in this tissue.
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Affiliation(s)
- K K Bradley
- Department of Pharmacology, University of Nevada, Reno, Nevada 89557, USA
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Okawa T, Syal AS, Vedernikov YP, Saade GR, Chwalisz K, Garfield RE. The effects of nitric oxide on the contractility of isolated uterine and aortic rings from pregnant rats. Am J Obstet Gynecol 1998; 179:721-6. [PMID: 9757978 DOI: 10.1016/s0002-9378(98)70071-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVE The object was to compare the effects of nitric oxide on isolated uterus and aorta of pregnant rats. STUDY DESIGN Rings of uterus and thoracic aorta without endothelium from Sprague-Dawley rats at mid and late gestation were used for isometric tension recording. The concentration-response curve for diethylamine/nitric oxide was studied in the presence or absence of oxyhemoglobin (10(-5) mol/L), or oxyhemoglobin was added after the response to diethylamine/nitric oxide. RESULTS Diethylamine/nitric oxide concentration dependently inhibited uterine contractions, and the effect was attenuated by previous treatment with oxyhemoglobin at mid gestation (n = 8). The effects were negligible at late gestation (n = 8). The relaxation of aortic rings by diethylamine/nitric oxide and its attenuation by previous treatment with oxyhemoglobin were similar at mid (n = 6) and late (n = 6) gestation. The sensitivity of aortic rings to diethylamine/nitric oxide is significantly higher than that of uterine rings. Oxyhemoglobin partly restored inhibited diethylamine/nitric oxide phenylephrine tension in aortic rings and had no effect on diethylamine/nitric oxide-inhibited uterine rings. CONCLUSIONS Uterine smooth muscle is less sensitive to nitric oxide than is aortic smooth muscle. Nitric oxide sensitivity of rat uterus but not aorta decreases toward term.
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Affiliation(s)
- T Okawa
- University of Texas Medical Branch, Galveston 77555-1062, USA
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Boquet M, Cebral E, Motta A, Berón de Astrada M, Gimeno MA. Relationship between mouse uterine contractility, nitric oxide and prostaglandin production in early pregnancy. Prostaglandins Leukot Essent Fatty Acids 1998; 59:163-7. [PMID: 9844987 DOI: 10.1016/s0952-3278(98)90057-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Despite the evidence for a functional role of nitric oxide (NO) in the regulation of uterine contractility in several species, there is little information about the effects of this gas on the mouse uterus. The aims of this study were to investigate if the NO relaxation pathway is present in mouse pregnant uterus and the relationship with the uterotonic prostaglandins (PGs E and F2alpha) production. We evaluated the effect of the treatment with a competitive nitric oxide synthase (NOs) inhibitor: N(G)-monomethyl-L-arginine on the spontaneous contractile activity and prostaglandin production on two different days of pregnancy: second day of pregnancy (preimplantation stage) and on the afternoon of the fifth day of pregnancy (postimplantation stage). We found that only on the fifth day of pregnancy did the inhibitor induce a highly significant isometric developed tension (IDT) and that this effect was maintained throughout the experiment. In order to evaluate if the generation of NO was also different between the two days of pregnancy, NOs activity was measured. Total NOs activity was significantly elevated during the postimplantation stage. We studied the interaction between the NO and cyclooxygenase (COX) pathways on the fifth day of pregnancy, and the data show no stimulation of PGs production by endogenous NO. In summary, we found that NO participates in the control of uterine contractility on the fifth day (a postimplantation stage) and that in this condition the NO was not able to elicit an increase in PGs production.
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Affiliation(s)
- M Boquet
- Centro de Estudios Farmacológicos y Botánicos, Consejo Nacional de Investigaciones Cientificas y Técnicas, Buenos Aires, Argentina
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Abstract
1. We evaluated the effect of the nitric oxide (NO) donor CysNO (S-nitroso-L-cysteine) and endogenous NO upon spontaneous contractility in non-pregnant cynomolgus monkeys. We also assessed the role of intracellular guanosine 3',5'-cyclic monophosphate ([cyclic GMP]i) as a second messenger for NO in monkey uterine smooth muscle. 2. CysNO reduced spontaneous contractility by 84% (P < 0.05) at maximal concentrations, and significantly elevated [cyclic GMP]i (P < 0.05). However, increases in [cyclic GMP]i were not required for CysNO-induced relaxations; CysNO inhibited contractile activity despite the complete inhibition of guanylyl cyclase by methylene blue or LY83,583. 3. Analogues of cyclic GMP had no significant effect upon spontaneous contractile activity. L-arginine produced a 62% reduction in spontaneous activity (P < 0.05) while D-arginine had no effect. The competitive nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine (L-NOARG) not only blocked L-arginine-induced relaxations, but also significantly increased spontaneous contractile activity when added alone (P < 0.05); the inactive D-enantiomer of NOARG had no such effect. 4. While both endogenous NO and the NO donor CysNO relax monkey myometrium, this effect is not causally related to CysNO-induced elevations in [cyclic GMP]i. The failure of cyclic GMP analogues to alter monkey uterine smooth muscle tension also argues against a role for [cyclic GMP]i in the regulation of uterine contractility. Not only do these findings argue for the existence of a functionally-relevant NOS in the monkey uterus, but increases in contractile activity seen in the presence of NOS inhibitors suggest a role for NO in the moment-to-moment regulation of contractile activity in this organ.
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Affiliation(s)
- K A Kuenzli
- Department of Pharmacology, University of Nevada, Reno 89577-0046, USA
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Hennan JK, Diamond J. Evidence that spontaneous contractile activity in the rat myometrium is not inhibited by NO-mediated increases in tissue levels of cyclic GMP. Br J Pharmacol 1998; 123:959-67. [PMID: 9535026 PMCID: PMC1565234 DOI: 10.1038/sj.bjp.0701678] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
1. There is conflicting evidence in the literature concerning the role of cyclic GMP in the regulation of myometrial contractility and the importance of hormonal status on the uterine response to cyclic GMP-elevating agents. The objective of the present study was to investigate further the importance of cyclic GMP in the control of uterine contractility, by monitoring the effects of cyclic GMP-elevating agents on spontaneous contractions and cyclic GMP levels in myometrial strips from pregnant rats and from ovariectomized rats under the influence of oestrogen and/or progesterone. 2. Sodium nitroprusside (SNP) 5 mM, atrial natriuretic peptide (ANP) 100 nM, L-arginine 1 mM and 8-bromo-cyclic GMP 100 mM had no relaxant effect on the spontaneous contractions of myometria from pregnant rats or from ovariectomized rats under the influence of oestrogen or progesterone. 3. Tissue levels of cyclic GMP were significantly elevated by SNP in all treatment groups, including pregnant animals. For example, in ovariectomized, progesterone-treated rats, SNP raised cyclic GMP levels approximately 8 fold from a basal level of 2.9 +/- 0.4 pmol mg(-1) protein to 24.8 +/- 4.0 pmol mg(-1) protein. ANP increased cyclic GMP levels approximately 2 fold in all treatment groups, except in the pregnant animals. L-Arginine elevated cyclic GMP significantly only in ovariectomized, vehicle-treated myometria. 4. The activity of cyclic GMP-dependent protein kinase (PKG) was significantly increased (3 fold) in myometria exposed to SNP (5 mM). Thus, the inability of SNP to relax uterine preparations was not due to a failure of SNP-elevated cyclic GMP to activate PKG. 5. The more potent NO donor, S-nitroso-N-acetylpenicillamine (SNAP), at a concentration of 100 microM was able to inhibit spontaneous contractions significantly in myometrial preparations from both non-ovariectomized and ovariectomized rats treated with oestrogen or progesterone. 6. Tissue levels of cyclic GMP were markedly increased by SNAP at concentrations of 10, 30 and 100 microM. At 100 microM, cyclic GMP levels increased from 1.9 +/- 0.2 pmol mg(-1) protein to 74.0 +/- 18.0 pmol mg(-1) protein. However, complete or partial blockade of SNAP-induced increases in cyclic GMP levels by the soluble guanylyl cyclase inhibitor, ODQ (25 microM), had no effect on the relaxant response to SNAP. Thus, the relaxant effect of SNAP in this tissue appears to be mediated via a mechanism independent of cyclic GMP. 7. Taken as a whole, the results of the present study indicate that cyclic GMP does not play an important role in the control of contractility in the rat uterus.
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Affiliation(s)
- J K Hennan
- Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada
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