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Porta M, Boening A, Tiemann J, Zack A, Patel A, Sondgeroth K. The Contractile Response to Oxytocin in Non-pregnant Rat Uteri Is Modified After the First Pregnancy. Reprod Sci 2023; 30:2152-2165. [PMID: 36696040 PMCID: PMC10310576 DOI: 10.1007/s43032-023-01163-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 12/24/2022] [Indexed: 01/26/2023]
Abstract
During pregnancy, the uterus undergoes several modifications under the influence of hormonal and mechanical stimuli. We hypothesize that while most of these modifications are reverted during involution, some of the physiological properties of the uterus are permanently altered. To investigate this hypothesis, we conducted motility experiments to evaluate the contractility response of uterine tissue samples from non-pregnant virgin and proven breeder female rats to oxytocin (10-10 to 10-5 M). We found that the virgin tissue contracts more robustly than proven breeder tissue in the absence of oxytocin, yet with oxytocin, proven breeder samples displayed a significantly higher increase in activity. These results could depend on a more elevated expression of oxytocin receptor and/or on an alteration in the intracellular pathways affected by the activation of the oxytocin receptors. Here, we explored the impact of some structures involved in the management of intracellular calcium on the dose response to oxytocin recorded from virgin and proven breeder uterine strips. Specifically, we replicated the dose response experiments in low extracellular calcium (10 μM), in the presence of the intracellular calcium channel blocker ruthenium red (10 μM), and in the presence of the sarcoplasmic-endoplasmic reticulum calcium ATP-ase pump inhibitor, cyclopiazonic acid (10 μM). The results of these experiments suggest that also the expression of proteins that control intracellular calcium availability is affected by the experience of pregnancy. Molecular biology experiments will give us more detail on the magnitude of these expression changes.
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Affiliation(s)
- Maura Porta
- Department of Physiology, College of Graduate Studies, Midwestern University, Downers Grove, IL 60515 USA
| | - Amber Boening
- Master of Biomedical Sciences Program, Midwestern University, Downers Grove, IL 60515 USA
| | - Jonathan Tiemann
- Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, IL 60515 USA
| | - Adam Zack
- Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, IL 60515 USA
| | - Arjun Patel
- Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, IL 60515 USA
| | - Korie Sondgeroth
- Department of Physiology, College of Graduate Studies, Midwestern University, Downers Grove, IL 60515 USA
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2
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Malik M, Roh M, England SK. Uterine contractions in rodent models and humans. Acta Physiol (Oxf) 2021; 231:e13607. [PMID: 33337577 PMCID: PMC8047897 DOI: 10.1111/apha.13607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 12/07/2020] [Accepted: 12/11/2020] [Indexed: 12/18/2022]
Abstract
Aberrant uterine contractions can lead to preterm birth and other labour complications and are a significant cause of maternal morbidity and mortality. To investigate the mechanisms underlying dysfunctional uterine contractions, researchers have used experimentally tractable small animal models. However, biological differences between humans and rodents change how researchers select their animal model and interpret their results. Here, we provide a general review of studies of uterine excitation and contractions in mice, rats, guinea pigs, and humans, in an effort to introduce new researchers to the field and help in the design and interpretation of experiments in rodent models.
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Affiliation(s)
- Manasi Malik
- Center for Reproductive Health Sciences Department of Obstetrics and Gynecology Washington University School of Medicine St. Louis MO USA
| | - Michelle Roh
- Center for Reproductive Health Sciences Department of Obstetrics and Gynecology Washington University School of Medicine St. Louis MO USA
| | - Sarah K. England
- Center for Reproductive Health Sciences Department of Obstetrics and Gynecology Washington University School of Medicine St. Louis MO USA
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Bafor EE, Ukpebor F, Omoruyi O, Ochoyama E, Omogiade G, Ekufu J, Edrada-Ebel R. Tocolytic activity assessment of the methanol leaf extract of Justicia flava Vahl (Acanthaceae) on mouse myometrial contractility and preliminary mass spectrometric determination of secondary metabolites. JOURNAL OF ETHNOPHARMACOLOGY 2019; 243:112087. [PMID: 31310827 DOI: 10.1016/j.jep.2019.112087] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Revised: 06/26/2019] [Accepted: 07/12/2019] [Indexed: 06/10/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE The leaves of Justicia flava are traditionally used in the South of Nigeria to prevent preterm births. AIM OF THE STUDY In this study, the activity of the methanol leaf extract of J. flava (JF) was investigated on uterine contractility in non-pregnant and pregnant isolated mouse tissues. MATERIAL AND METHODS The effects on spontaneous, oxytocin, and KCl-induced contractions were determined. The effects in calcium-free media were also determined. Possible mechanisms of activity were investigated using receptor and channel modulators. Mass spectrometric analysis was additionally performed on the leaf extract to identify secondary metabolites. RESULTS JF was observed to inhibit spontaneous, oxytocin and high KCl-induced uterine contractility. JF also inhibited contractions in Ca2+-free media. JF was found to exert its inhibitory effect via interaction with inositol triphosphate and ryanodine receptors and also through modulation of K+- channels. Lignans and alkaloids were identified with the lignans being the most abundant in JF. CONCLUSION JF has been shown to potently inhibit uterine contractions in non-pregnant and pregnant isolated mouse uterus. The inhibitory activity of JF has been shown to occur via blockade of extracellular and intracellular calcium entry and these effects may be due to the lignans identified in - JF. JF has therefore been shown in this study to be a lead plant in the discovery of new drugs with uterine inhibitory activity.
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Affiliation(s)
- Enitome E Bafor
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, University of Benin, Benin City, Nigeria.
| | - Faith Ukpebor
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, University of Benin, Benin City, Nigeria.
| | - Osemelomen Omoruyi
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, University of Benin, Benin City, Nigeria
| | - Ejiro Ochoyama
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, University of Benin, Benin City, Nigeria
| | - Glory Omogiade
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, University of Benin, Benin City, Nigeria
| | - Jude Ekufu
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, University of Benin, Benin City, Nigeria
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Xiong Z, Lang L, Gao X, Xiao W, Wang Z, Zhao L. An integrative urinary metabolomic study of the therapeutic effect of Guizhi Fuling capsule on primary dysmenorrheal rats based 1H NMR and UPLC–MS. J Pharm Biomed Anal 2019; 164:750-758. [DOI: 10.1016/j.jpba.2018.11.039] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 11/15/2018] [Accepted: 11/16/2018] [Indexed: 01/19/2023]
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5
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Zowalaty AEE, Ye X. Seipin deficiency leads to defective parturition in mice. Biol Reprod 2018; 97:378-386. [PMID: 29088395 DOI: 10.1093/biolre/iox088] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 08/10/2017] [Indexed: 01/28/2023] Open
Abstract
Seipin is an integral endoplasmic reticulum membrane protein encoded by Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2/Bscl2) gene. Seipin deficiency results in lipodystrophy, diabetes, muscle hypertrophy, and male infertility in both human and mouse. Seipin function in female reproduction is unknown. Bscl2-/- dams had normal embryo implantation and body weight gain during pregnancy but reduced delivery rates from 2nd to 4th pregnancies and reduced numbers of pups delivered from 1st to 4th pregnancies. Characterization of first pregnancy revealed increased gestation period and parturition problems, including uterine prolapse, difficulty in delivery, undelivered fetuses, and undelivered tissues in Bscl2-/- females. Bscl2-/- uterine weight was comparable to control at 3 weeks old but significantly increased with myometrial hypertrophy at 10 months old. In situ hybridization revealed relatively low level of Bscl2 mRNA expression in myometrium throughout pregnancy and postpartum but high level of expression in uterine luminal epithelium, suggesting that systemic effect (e.g. elevated glucose and insulin levels) rather than local seipin-deficiency in myometrium might be a main contributing factor to myometrial hypertrophy. On near-term gestation day 18.5 (D18.5), Bscl2-/- females had normal levels of serum progesterone and 17β-estradiol, indicating functional ovary and placenta. Proliferating Cell Nuclear Antigen (PCNA) staining showed minimal myometrial cell proliferation in both D18.5 Bscl2+/+ and Bscl2-/- uteri. There was strong LC3 immunostaining in Bscl2+/+ and Bscl2-/- peripartum myometrium and increased LC3 staining in Bscl2-/- peripartum uterine luminal epithelium, suggesting a potential role of seipin in regulating autophagy in uterine luminal epithelium but not myometrium. This study demonstrates an association of seipin with myometrium and parturition.
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Affiliation(s)
- Ahmed E El Zowalaty
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.,Interdisciplinary Toxicology Program, University of Georgia, Athens, Georgia, United States of America
| | - Xiaoqin Ye
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.,Interdisciplinary Toxicology Program, University of Georgia, Athens, Georgia, United States of America
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Lang L, Meng Z, Sun L, Xiao W, Zhao L, Xiong Z. Intergrated metabonomic study of the effects of Guizhi Fuling capsule intervention on primary dysmenorrheal using RP-UPLC-MS complementary with HILIC-UPLC-MS technique. Biomed Chromatogr 2017; 32. [PMID: 28906007 DOI: 10.1002/bmc.4093] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/23/2017] [Accepted: 09/07/2017] [Indexed: 01/13/2023]
Abstract
Guizhi Fuling capsule (GFC), developed from the traditional Chinese prescription of Guizhi Fuling Wan, has been commonly used for the treatment of primary dysmenorrhea (PD). However, the intervention effective mechanism in vivo has not been well elucidated. In this study, an integrated plasma metabonomic strategy based on RP-UPLC-MS coupled with HILIC-UPLC-MS technique has been developed to investigate the global therapeutic effects and intervention mechanisms of GFC on dysmenorrhea rats induced by oxytocin. The 20 potential biomarkers were identified and primarily related to sphingolipid metabolism, steroid hormone biosynthesis, glycerophospholipid metabolism, amino acid metabolism, lipid metabolism and energy metabolism. The results showed that the GFC has therapeutic effects on rats with dysmenorrhea via the regulation of multiple metabolic pathways. Some new potential biomarkers associated with primary dysmenorrhea such as phenylalanine, tryptophan, taurine, carnitine, betaine, creatine and creatinine have been discovered in this study for the first time. This study provides a metabonomic platform based on RP-UPLC-MS complementary to HILIC-UPLC-MS technique to investigate both nonpolar and polar compounds, so as to get a more comprehensive metabolite information to yield insight into the pathophysiology of PD and assessing the efficacy of GFC on PD rats.
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Affiliation(s)
- Lang Lang
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, China
| | - Zhaorui Meng
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, China
| | - Lan Sun
- Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Research, China Pharmaceutical University, Nanjing, Jiangsu, China.,State Key Laboratory of New-tech for Chinese Medicine Pharmaceutic Process, Jiangsu Kanion Pharmaceutical Co. Ltd, Lianyungang, Jiangsu, China
| | - Wei Xiao
- Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Research, China Pharmaceutical University, Nanjing, Jiangsu, China.,State Key Laboratory of New-tech for Chinese Medicine Pharmaceutic Process, Jiangsu Kanion Pharmaceutical Co. Ltd, Lianyungang, Jiangsu, China
| | - Longshan Zhao
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, China.,State Key Laboratory of New-tech for Chinese Medicine Pharmaceutic Process, Jiangsu Kanion Pharmaceutical Co. Ltd, Lianyungang, Jiangsu, China
| | - Zhili Xiong
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, China
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7
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Functional involvement of protein kinase C, Rho-kinase and TRPC3 decreases while PLC increases with advancement of pregnancy in mediating oxytocin-induced myometrial contractions in water buffaloes ( Bubalus bubalis ). Theriogenology 2017; 92:176-189. [DOI: 10.1016/j.theriogenology.2016.12.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 12/06/2016] [Accepted: 12/06/2016] [Indexed: 11/20/2022]
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Arrowsmith S, Neilson J, Wray S. The combination tocolytic effect of magnesium sulfate and an oxytocin receptor antagonist in myometrium from singleton and twin pregnancies. Am J Obstet Gynecol 2016; 215:789.e1-789.e9. [PMID: 27555315 DOI: 10.1016/j.ajog.2016.08.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 08/01/2016] [Accepted: 08/09/2016] [Indexed: 11/30/2022]
Abstract
BACKGROUND Preterm birth at <37 weeks of gestation is the most common and costly complication of pregnancy and remains the leading cause of neonatal morbidity, death, and reduced achievement in surviving infants. Magnesium sulfate is 1 class of tocolytics for threatened preterm labor; however, its clinical efficacy has been questioned. Twin pregnancies are at increased risk of preterm delivery compared with singleton gestations, which suggests that there is twin-specific risk to preterm delivery in twins. The prevention strategies that are applied to singleton pregnancies, however, have not been shown to be effective in twin pregnancies. OBJECTIVE The purpose of this study was to compare the relaxant effect of magnesium sulfate on spontaneous and oxytocin-augmented contractions of human myometrium from singleton and twin pregnancies and to examine whether the effect of oxytocin on magnesium sulfate's potency could be reversed with the use of the oxytocin receptor antagonist, atosiban. STUDY DESIGN Myometrium was obtained at the time of prelabor cesarean section (36-40 weeks of gestation) from women with singleton (n=23) or twin (n=12) pregnancy. Isometric tension recordings were made on myometrial strips that were mounted in organ baths that were superfused with physiologic saline solution. Strips were exposed to rising concentrations of magnesium sulfate, and the effect on spontaneous contractions or stimulated with oxytocin (0.5 nmol/L) and in the presence or absence of atosiban (100 nmol/L) was recorded. The contractile characteristics after each application of magnesium sulfate, which included amplitude of contraction and activity integral, were measured. Concentration-response curves were fitted with the use of nonlinear regression and comparison of the negative logarithm of the 50% reduction in activity values. RESULTS Magnesium sulfate exerted an equal concentration-dependent inhibitory effect on spontaneous myometrial contractions from both singleton and twin myometrium (P>.05). The application of oxytocin produced a significant rightward shift in the concentration-response curves (P<.0001), but no differences were found between pregnancy groups (P>.05). The addition of atosiban shifted concentration-response curves significantly back to the left for amplitude of contraction and activity integral in singletons (P<.0001). However, only activity integral was significantly reversed in twins (P<.01). CONCLUSION Magnesium sulfate is equipotent in suppressing contractions in singleton and twin myometrium. Oxytocin (0.5 nmol/L) significantly reduces the tocolytic potency of magnesium sulfate, which may explain, in part, magnesium sulfate's poor efficacy in vivo; however, this can be reversed partially by the use of an oxytocin receptor antagonist. Combination tocolysis that involves oxytocin receptor antagonists requires further investigation.
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Affiliation(s)
- Sarah Arrowsmith
- Harris-Wellbeing Preterm Birth Research Centre, Department of Cellular and Molecular Physiology, the Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - James Neilson
- Department of Women's and Children's Health, the Institute of Translational Medicine, University of Liverpool, Liverpool, UK
| | - Susan Wray
- Harris-Wellbeing Preterm Birth Research Centre, Department of Cellular and Molecular Physiology, the Institute of Translational Medicine, University of Liverpool, Liverpool, UK
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Matthew A, Kupittayanant S, Burdyga T, Wray S. Characterization of Contractile Activity and Intracellular Ca2+ Signalling in Mouse Myometrium. ACTA ACUST UNITED AC 2016; 11:207-12. [PMID: 15120693 DOI: 10.1016/j.jsgi.2003.10.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVE To characterize the contractile responses of mouse myometrium, the associated calcium (Ca2+) changes and the role of the sarcoplasmic reticulum (SR), and to better understand excitation contraction coupling in this tissue. METHODS Strips of longitudinal myometrium were used, and Ca2+ was measured after loading with Indo-1. RESULTS Intracellular Ca2+ transients, produced by Ca2+ entry, preceded phasic spontaneous contractions. Depolarization with high potassium concentration significantly increased the amplitude of the contractions and transformed the pattern of activity from phasic to tonic, with accompanying changes in intracellular Ca2+ concentration ([Ca2+]i). Oxytocin significantly stimulated contractile activity and [Ca2+]i above the level occurring spontaneously. Thus all forms of contractile activity were closely correlated with Ca2+. When the SR was emptied using a blocker of the SR calcium-adenosinetriphosphatase, cyclopiazonic acid, spontaneous Ca2+ and force transients increased greatly in frequency and amplitude. Ryanodine, a blocker of Ca(2+)-induced Ca2+ release (CICR), did not impair activity. In the absence of external Ca2+, oxytocin was able to release Ca2+ from the SR through IP3 but produced only a small increase in force, demonstrating a requirement for Ca2+ entry as part of the mechanism of agonist action. CONCLUSION Mouse myometrium, (1) produces contractile activity reflecting changes in [Ca2+]i irrespective of the stimulus, (2) has a significant SR Ca2+ content releasable by agonists but not CICR, (3) has an SR acting to inhibit spontaneous activity, and (4) behaves qualitatively similarly to human and rat myometrium in major aspects of excitation contraction coupling and is therefore a useful model tissue.
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Affiliation(s)
- A Matthew
- Department of Physiology, The University of Liverpool, United Kingdom
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10
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Wray S, Burdyga T, Noble D, Noble K, Borysova L, Arrowsmith S. Progress in understanding electro-mechanical signalling in the myometrium. Acta Physiol (Oxf) 2015; 213:417-31. [PMID: 25439280 DOI: 10.1111/apha.12431] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 11/11/2014] [Accepted: 11/17/2014] [Indexed: 11/30/2022]
Abstract
In this review, we give a state-of-the-art account of uterine contractility, focussing on excitation-contraction (electro-mechanical) coupling (ECC). This will show how electrophysiological data and intracellular calcium measurements can be related to more modern techniques such as confocal microscopy and molecular biology, to advance our understanding of mechanical output and its modulation in the smooth muscle of the uterus, the myometrium. This new knowledge and understanding, for example concerning the role of the sarcoplasmic reticulum (SR), or stretch-activated K channels, when linked to biochemical and molecular pathways, provides a clearer and better informed basis for the development of new drugs and targets. These are urgently needed to combat dysfunctions in excitation-contraction coupling that are clinically challenging, such as preterm labour, slow to progress labours and post-partum haemorrhage. It remains the case that scientific progress still needs to be made in areas such as pacemaking and understanding interactions between the uterine environment and ion channel activity.
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Affiliation(s)
- S. Wray
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - T. Burdyga
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - D. Noble
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - K. Noble
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - L. Borysova
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - S. Arrowsmith
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
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11
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Sukwan C, Wray S, Kupittayanant S. The effects of Ginseng Java root extract on uterine contractility in nonpregnant rats. Physiol Rep 2014; 2:2/12/e12230. [PMID: 25472610 PMCID: PMC4332211 DOI: 10.14814/phy2.12230] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Ginseng Java or Talinum paniculatum (Jacq.) Geartn has long been used in herbal recipes because of its various therapeutic properties. Ginseng Java is believed to be beneficial to the female reproductive system by inducing lactation and restoring uterine functions after the postpartum period. There are, however, no scientific data on verifying the effects on the uterus to support its therapeutic relevance. Therefore, the purpose of this study was to investigate the effects of Ginseng Java root extract and its possible mechanism(s) of action on uterine contractility. Female virgin rats were humanely killed by CO2 asphyxia and uteri removed. Isometric force was measured in strips of longitudinal myometrium. The effects of Ginseng Java root extract at its IC50 concentration (0.23 mg/mL) on spontaneous, oxytocin‐induced (10 nmol/L), and depolarized (KCl 40 mmol/L) contraction were investigated. After establishing regular phasic contractions, the application of Java root extract significantly inhibited spontaneous uterine contractility (n =5). The extract also significantly inhibited the contraction induced by high KCl solution (n =5) and oxytocin (n =5). The extract also inhibited oxytocin‐induced contraction in the absence of external Ca entry (n =7) and the tonic force induced by oxytocin in the presence of high KCl solution. Taken together, the data demonstrate a potent and consistent ability of extract from Ginseng Java root to reduce myometrial contractility. The tocolytic effects were demonstrated on both spontaneous and agonist‐induced contractions. The fact that force was inhibited in depolarized conditions suggests that the possible mechanisms may be blockade of Ca influx via L‐type Ca channels. The data in Ca‐free solutions suggest that the extract also reduces IP3‐induced Ca release from the internal store. These tocolytic effects do not support the use of ginseng to help with postpartum contractility, but instead suggest it may be helpful in reducing inappropriate uterine contractions, such as in threatened preterm delivery. The data demonstrate a potent and consistent ability of extract from Ginseng Java root to reduce myometrial contractility. The tocolytic effects were demonstrated on both spontaneous and agonist‐induced contractions.
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Affiliation(s)
- Catthareeya Sukwan
- Agricultural Program, Faculty of Science and Technology, Nakhon Ratchasima Rajabhat University, Nakhon Ratchasima, Thailand
| | - Susan Wray
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, U.K
| | - Sajeera Kupittayanant
- School of Physiology, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand
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12
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Gravina FS, van Helden DF, Kerr KP, de Oliveira RB, Jobling P. Phasic contractions of the mouse vagina and cervix at different phases of the estrus cycle and during late pregnancy. PLoS One 2014; 9:e111307. [PMID: 25337931 PMCID: PMC4206458 DOI: 10.1371/journal.pone.0111307] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 09/30/2014] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND/AIMS The pacemaker mechanisms activating phasic contractions of vaginal and cervical smooth muscle remain poorly understood. Here, we investigate properties of pacemaking in vaginal and cervical tissues by determining whether: 1) functional pacemaking is dependent on the phase of the estrus cycle or pregnancy; 2) pacemaking involves Ca2+ release from sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) -dependent intracellular Ca2+ stores; and 3) c-Kit and/or vimentin immunoreactive ICs have a role in pacemaking. METHODOLOGY/PRINCIPAL FINDINGS Vaginal and cervical contractions were measured in vitro, as was the distribution of c-Kit and vimentin positive interstitial cells (ICs). Cervical smooth muscle was spontaneously active in estrus and metestrus but quiescent during proestrus and diestrus. Vaginal smooth muscle was normally quiescent but exhibited phasic contractions in the presence of oxytocin or the K+ channel blocker tetraethylammonium (TEA) chloride. Spontaneous contractions in the cervix and TEA-induced phasic contractions in the vagina persisted in the presence of cyclopiazonic acid (CPA), a blocker of the SERCA that refills intracellular SR Ca2+ stores, but were inhibited in low Ca2+ solution or in the presence of nifedipine, an inhibitor of L-type Ca2+channels. ICs were found in small numbers in the mouse cervix but not in the vagina. CONCLUSIONS/SIGNIFICANCE Cervical smooth muscle strips taken from mice in estrus, metestrus or late pregnancy were generally spontaneously active. Vaginal smooth muscle strips were normally quiescent but could be induced to exhibit phasic contractions independent on phase of the estrus cycle or late pregnancy. Spontaneous cervical or TEA-induced vaginal phasic contractions were not mediated by ICs or intracellular Ca2+ stores. Given that vaginal smooth muscle is normally quiescent then it is likely that increases in hormones such as oxytocin, as might occur through sexual stimulation, enhance the effectiveness of such pacemaking until phasic contractile activity emerges.
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Affiliation(s)
- Fernanda S. Gravina
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Dirk F. van Helden
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Karen P. Kerr
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Ramatis B. de Oliveira
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Phillip Jobling
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
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13
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Arrowsmith S, Wray S. Oxytocin: its mechanism of action and receptor signalling in the myometrium. J Neuroendocrinol 2014; 26:356-69. [PMID: 24888645 DOI: 10.1111/jne.12154] [Citation(s) in RCA: 161] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 03/14/2014] [Accepted: 03/28/2014] [Indexed: 12/17/2022]
Abstract
Oxytocin is a nonapeptide hormone that has a central role in the regulation of parturition and lactation. In this review, we address oxytocin receptor (OTR) signalling and its role in the myometrium during pregnancy and in labour. The OTR belongs to the rhodopsin-type (Class 1) of the G-protein coupled receptor superfamily and is regulated by changes in receptor expression, receptor desensitisation and local changes in oxytocin concentration. Receptor activation triggers a number of signalling events to stimulate contraction, primarily by elevating intracellular calcium (Ca(2+) ). This includes inositol-tris-phosphate-mediated store calcium release, store-operated Ca(2+) entry and voltage-operated Ca(2+) entry. We discuss each mechanism in turn and also discuss Ca(2+) -independent mechanisms such as Ca(2+) sensitisation. Because oxytocin induces contraction in the myometrium, both the activation and the inhibition of its receptor have long been targets in the management of dysfunctional and preterm labours, respectively. We discuss current and novel OTR agonists and antagonists and their use and potential benefit in obstetric practice. In this regard, we highlight three clinical scenarios: dysfunctional labour, postpartum haemorrhage and preterm birth.
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Affiliation(s)
- S Arrowsmith
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
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14
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Illanes SE, Pérez-Sepúlveda A, Rice GE, Mitchell MD. Preterm labour: association between labour physiology, tocolysis and prevention. Expert Opin Investig Drugs 2014; 23:759-71. [PMID: 24717074 DOI: 10.1517/13543784.2014.905541] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION In developed countries, preterm birth is the major cause of perinatal morbidity, mortality and the most important public health problem in the obstetric field. In the past decades, an increasing trend has been observed regardless of the great efforts focussed on the improvement of our understanding of the physiopathological mechanisms behind preterm labour (PTL) and the improvement in the use of tocolytic drugs. AREAS COVERED In this review, the authors focus on some points of the physiopathology of labour in order to understand the rationality behind the different management approaches developed for the PTL syndrome. EXPERT OPINION There is a need to develop new tools for the treatment of patients with PTL. Research focussed on improving tocolysis, the physiology of labour and pathological processes involved in PTL would afford new approaches for the treatment of PTL, allowing clinicians to provide integrative solutions for this multifactorial disease. Recently, the prophylactic use of progesterone pessary and cerclage in women with high risk of premature labour has been reported to reduce the incidence of premature births and improve neonatal outcomes. These results highlight the importance of prediction models in order to establish preventative strategies early in pregnancy.
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Affiliation(s)
- Sebastián E Illanes
- Universidad de Los Andes, Department of Obstetrics & Gynaecology and Laboratory of Reproductive Biology, Faculty of Medicine , Santiago , Chile
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15
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Abstract
BACKGROUND Understanding the physiology of pregnancy enables effective management of pregnancy complications that could otherwise be life threatening for both mother and fetus. A functional uterus (i) retains the fetus in utero during pregnancy without initiating stretch-induced contractions and (ii) is able to dilate the cervix and contract the myometrium at term to deliver the fetus. The onset of labour is associated with successful cervical remodelling and contraction of myometrium, arising from concomitant activation of uterine immune and endocrine systems. A large body of evidence suggests that actions of local steroid hormones may drive changes occurring in the uterine microenvironment at term. Although there have been a number of studies considering the potential role(s) played by progesterone and estrogen at the time of parturition, the bio-availability and effects of androgens during pregnancy have received less scrutiny. The aim of this review is to highlight potential roles of androgens in the biology of pregnancy and parturition. METHODS A review of published literature was performed to address (i) androgen concentrations, including biosynthesis and clearance, in maternal and fetal compartments throughout gestation, (ii) associations of androgen concentrations with adverse pregnancy outcomes, (iii) the role of androgens in the physiology of cervical remodelling and finally (iv) the role of androgens in the physiology of myometrial function including any impact on contractility. RESULTS Some, but not all, androgens increase throughout gestation in maternal circulation. The effects of this increase are not fully understood; however, evidence suggests that increased androgens might regulate key processes during pregnancy and parturition. For example, androgens are believed to be critical for cervical remodelling at term, in particular cervical ripening, via regulation of cervical collagen fibril organization. Additionally, a number of studies highlight potential roles for androgens in myometrial relaxation via non-genomic, AR-independent pathways critical for the pregnancy reaching term. Understanding of the molecular events leading to myometrial relaxation is an important step towards development of novel targeted tocolytic drugs. CONCLUSIONS The increase in androgen levels throughout gestation is likely to be important for establishment and maintenance of pregnancy and initiation of parturition. Further investigation of the underlying mechanisms of androgen action on cervical remodelling and myometrial contractility is needed. The insights gained may facilitate the development of new therapeutic approaches to manage pregnancy complications such as preterm birth.
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Affiliation(s)
- Sofia Makieva
- Medical Research Council Centre for Reproductive Health, The University of Edinburgh, Queen's Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom and Tommy's Centre for Maternal and Fetal Health, University of Edinburgh, Queen's Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom
| | - Philippa T K Saunders
- Medical Research Council Centre for Reproductive Health, The University of Edinburgh, Queen's Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom and
| | - Jane E Norman
- Medical Research Council Centre for Reproductive Health, The University of Edinburgh, Queen's Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom and Tommy's Centre for Maternal and Fetal Health, University of Edinburgh, Queen's Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom
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16
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Kupittayanant S, Munglue P, Lijuan W, Promprom W, Budhaklala N, Wray S. Finding new agents in medicinal plants to act on the myometrium. Exp Physiol 2014; 99:530-7. [DOI: 10.1113/expphysiol.2013.072884] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Sajeera Kupittayanant
- Institute of Science; Suranaree University of Technology; Muang District Nakhon Ratchasima Thailand
| | - Phukphon Munglue
- Faculty of Science; Ubon Ratchathani Rajabhat University; Muang District Ubon Ratchathani Thailand
| | - Wanwisa Lijuan
- Faculty of Science and Technology; Thepsatri Rajabhat University; Muang Lop Buri Lobburi Thailand
| | - Wilawan Promprom
- Faculty of Science; Mahasarakham University; Kantrawichai Mahasarakham Thailand
| | - Nopparat Budhaklala
- Faculty of Science; Rajamangala University of Technology Thanyaburi; Thanyaburi Pathum Thani Thailand
| | - Susan Wray
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool UK
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17
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Pehlivanoğlu B, Bayrak S, Doğan M. A close look at the contraction and relaxation of the myometrium; the role of calcium. J Turk Ger Gynecol Assoc 2013; 14:230-4. [PMID: 24592112 DOI: 10.5152/jtgga.2013.67763] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 08/12/2013] [Indexed: 11/22/2022] Open
Abstract
The function and regulation of the myometrium, especially during pregnancy, labour and birth are important in reproductive physiology. It is crucial to understand the mechanisms that generate and modulate uterine contractility in order to be able to prevent and/or treat the problems related with the myometrium. A limited understanding of the cellular and molecular events underlying these phenomena complicates the situation. Various agonists, hormones, transmitters and/or chemicals are related to the regulation of the functions of the myometrium. Although notable advances regarding the key steps in receptor signalling explaining the actions of these factors have been achieved, a good deal of information is still necessary to understand this vital process. A better comprehension of myometrium physiology and the translation of research findings to clinical settings will help progress in women's health. In this review, we attempt to present a critical overview of myometrial functions and focus specifically on the role of calcium.
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Affiliation(s)
- Bilge Pehlivanoğlu
- Department of Physiology, Hacettepe University Faculty of Medicine, Ankara, Turkey
| | - Sibel Bayrak
- Department of Physiology, Hacettepe University Faculty of Medicine, Ankara, Turkey
| | - Murat Doğan
- Department of Physiology, Hacettepe University Faculty of Medicine, Ankara, Turkey
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18
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Chen Y, Cao Y, Xie Y, Zhang X, Yang Q, Li X, Sun J, Qiu P, Cao W, Wang S. Traditional Chinese medicine for the treatment of primary dysmenorrhea: how do Yuanhu painkillers effectively treat dysmenorrhea? PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2013; 20:1095-1104. [PMID: 23806889 DOI: 10.1016/j.phymed.2013.05.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 04/15/2013] [Accepted: 05/19/2013] [Indexed: 06/02/2023]
Abstract
AIM To examine the efficacy of YuanHu painkillers (YHP) as a treatment for primary dysmenorrhea and to reveal YHP's principle formula. METHODS A Wistar rat uterine contraction model was utilized in this study. Rats were given 0.698g/kg YHP, 0.07g/kg tetrahydropalmatine (THP; YHP's main component), 0.02g/kg imperatorin (IMP), or THP+IMP (0.07+0.02g/kg) as polypharmacy (PG) by gavage. H&E staining and histopathological examination of the uteri tissue samples were performed. We then detected superoxide dismutase (SOD) and malondialdehyde (MDA), nitric oxide (NO), as well as inducible nitric oxide synthase (iNOS), i-κB, nuclear factor-κB (NF-κB), and cyclooxygenase-2 (COX-2) indices. RESULTS PG significantly inhibited the uterine contraction of the primary dysmenorrhea rat model (p<0.05), and was significantly different than single-agent therapy (p<0.05). Histopathological examination showed inflammation in the uteri of the control group which YHP and its main constitutes alleviated. THP significantly inhibited the contraction of isolated uteri caused by Ach, PGF2α and oxytocin in a concentration-dependent fashion. THP and IMP both significantly affected the levels of NO, activation of NF-κB, up-regulated the expression of i-κB and down-regulated the expression of both iNOS and COX-2. IMP obviously decreased the level of MDA and increased the activation of SOD (p<0.05). PG obviously improved all the parameters mentioned above (p<0.05). CONCLUSIONS YHP exerted protective effects on primary dysmenorrhea in rats and remarkably alleviated the severity of experimental primary dysmenorrhea. The combined strategy proved to be more effective than either THP or IMP alone and may have synergistic effects in combination in primary dysmenorrhea. Mechanisms that might account for the beneficial effects include abating oxidative stress, inhibiting over-inflammatory reaction, and alleviating the contraction of isolated rat uteri by inhibiting the influx of extracellular Ca(2+). Broad potential for future clinical practice is foreseeable.
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Affiliation(s)
- Yuetao Chen
- Institute of Materia Medica, School of Pharmacy, Fourth Military Medical University, Xi'an 710032, China.
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19
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Turton P, Arrowsmith S, Prescott J, Ballard C, Bricker L, Neilson J, Wray S. A comparison of the contractile properties of myometrium from singleton and twin pregnancies. PLoS One 2013; 8:e63800. [PMID: 23671701 PMCID: PMC3646038 DOI: 10.1371/journal.pone.0063800] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 04/05/2013] [Indexed: 12/02/2022] Open
Abstract
Objective Over half of twin pregnancies in US and UK deliver prematurely but the reasons for this are unclear. The contractility of myometrium from twin pregnancies has not been directly investigated. The objective of this research was to determine if there are differences in the contractile activity and response to oxytocin, between myometrium from singleton and twin pregnancies, across a range of gestational ages. Furthermore, we wished to determine if contractile activity correlates with increasing level of stretch, using neonatal birth weights as a marker of uterine stretch. Methods This was an in vitro, laboratory based study of myometrial contractility in women pregnant with one or two babies, using biopsies obtained from non-labouring women undergoing Caesarean section. Spontaneous, oxytocin-stimulated and depolarization induced contractile activity was compared. Results Direct measurements of myometrial contractility under controlled conditions show that the frequency of contractions and responses to oxytocin are significantly increased in twins compared to singletons. The duration of contraction however was significantly reduced. We find that contractile activity correlates with increasing levels of stretch, using neonatal birth weights as a surrogate for uterine stretch, with response to oxytocin being significantly positively correlated with birth weight. Conclusions We have found significant differences in contractile properties between myometrium from singleton and twin pregnancies and that increasing uterine stretch can alter the contractile properties of myometrium. We discuss the implication of these findings to preterm delivery and future studies.
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Affiliation(s)
- Peter Turton
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Sarah Arrowsmith
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Jonathan Prescott
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Celia Ballard
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Leanne Bricker
- Liverpool Women's NHS Foundation Trust, Liverpool, United Kingdom
| | - James Neilson
- Department of Women's and Children's Health, Institute of Translational Medicine, University of Liverpool, United Kingdom
| | - Susan Wray
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
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20
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Tykocki NR, Thompson JM, Jackson WF, Watts SW. Ryanodine receptors are uncoupled from contraction in rat vena cava. Cell Calcium 2012. [PMID: 23177664 DOI: 10.1016/j.ceca.2012.10.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ryanodine receptors (RyR) are Ca(2+)-sensitive ion channels in the sarcoplasmic reticulum (SR) membrane, and are important effectors of SR Ca(2+) release and smooth muscle excitation-contraction coupling. While the relationship between RyR activation and contraction is well characterized in arteries, little is known about the role of RyR in excitation-contraction coupling in veins. We hypothesized that RyR are present and directly coupled to contraction in rat aorta (RA) and vena cava (RVC). RA and RVC expressed mRNA for all 3 RyR subtypes, and immunofluorescence showed RyR protein was present in RA and RVC smooth muscle cells. RA and RVC rings contracted when Ca(2+) was re-introduced after stores depletion with thapsigargin (1μM), indicating both tissues contained intracellular Ca(2+) stores. To assess RyR function, contraction was then measured in RA and RVC exposed to the RyR activator caffeine (20mM). In RA, caffeine caused contraction that was attenuated by the RyR antagonists ryanodine (10μM) and tetracaine (100μM). However, caffeine (20mM) did not contract RVC. We next measured contraction and intracellular Ca(2+) (Ca(2+)(i)) simultaneously in RA and RVC exposed to caffeine. While caffeine increased Ca(2+)(i) and contracted RA, it had no significant effect on Ca(2+)(i) or contraction in RVC. These data suggest that ryanodine receptors, while present in both RA and RVC, are inactive and uncoupled from Ca(2+) release and contraction in RVC.
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Affiliation(s)
- N R Tykocki
- Department of Pharmacology and Toxicology, Michigan State University, 1355 Bogue St. Room B-445, East Lansing, MI 48824, USA.
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21
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Robinson H, Wray S. A new slow releasing, H₂S generating compound, GYY4137 relaxes spontaneous and oxytocin-stimulated contractions of human and rat pregnant myometrium. PLoS One 2012; 7:e46278. [PMID: 23029460 PMCID: PMC3459845 DOI: 10.1371/journal.pone.0046278] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 08/29/2012] [Indexed: 12/16/2022] Open
Abstract
Better tocolytics are required to help prevent preterm labour. The gaseotransmitter Hydrogen sulphide (H2S) has been shown to reduce myometrial contractility and thus is of potential interest. However previous studies used NaHS, which is toxic and releases H2S as a non-physiological bolus and thus alternative H2S donors are sought. GYY4137 has been developed to slowly release H2S and hence better reflect endogenous physiological release. We have examined its effects on spontaneous and oxytocin-stimulated contractility and compared them to NaHS, in human and rat myometrium, throughout gestation. The effects on contractility in response to GYY4137 (1 nM–1 mM) and NaHS (1 mM) were examined on myometrial strips from, biopsies of women undergoing elective caesarean section or hysterectomy, and from non-pregnant, 14, 18, 22 day (term) gestation or labouring rats. In pregnant rat and human myometrium dose-dependent and significant decreases in spontaneous contractions were seen with increasing concentrations of GYY4137, which also reduced underlying Ca transients. GYY4137 and NaHS significantly reduced oxytocin-stimulated and high-K depolarised contractions as well as spontaneous activity. Their inhibitory effects increased as gestation advanced, but were abruptly reversed in labour. Glibenclamide, an inhibitor of ATP-sensitive potassium (KATP) channels, abolished the inhibitory effect of GYY4137. These data suggest (i) H2S contributes to uterine quiescence from mid-gestation until labor, (ii) that H2S affects L-type calcium channels and KATP channels reducing Ca entry and thereby myometrial contractions, (iii) add to the evidence that H2S plays a physiological role in relaxing myometrium, and thus (iv) H2S is an attractive target for therapeutic manipulation of human myometrial contractility.
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Affiliation(s)
- Hayley Robinson
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Susan Wray
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
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22
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Munglue P, Eumkep G, Wray S, Kupittayanant S. The effects of watermelon (Citrullus lanatus) extracts and L-citrulline on rat uterine contractility. Reprod Sci 2012; 20:437-48. [PMID: 22991380 DOI: 10.1177/1933719112459223] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In uterine smooth muscle, the effects of watermelon and its citrulline content are unknown. The aims of this study were therefore, to determine the effects of watermelon extract and citrulline on the myometrium and to investigate their mechanisms of action. The effects of extracts of watermelon flesh and rind and L-citrulline (64 μmol/L) were evaluated on 3 types of contractile activity; spontaneous, those elicited by potassium chloride (KCl) depolarization, or oxytocin (10 nmol/L) application in isolated rat uterus. Inhibitors of nitric oxide (NO) and its mechanisms of action, N ω-Nitro-L-arginine methyl ester hydrochloride (L-NAME, 100 μmol/L), LY83583 (1 μmol/L), and tetraethylamonium chloride (5 mmol/L), as well as Ca signaling pathways, were determined. Both flesh and rind extracts significantly decreased the force produced by all 3 mechanisms, in a dose-dependent manner. The extracts could also significantly decrease the force under conditions of sustained high Ca levels (depolarization and agonist) and when the force was produced only by sarcoplasmic reticulum (SR) Ca release. L-citrulline produced the same effects on force as watermelon extracts. With submaximal doses of extract, the additive effects of L-citrulline were found. The inhibitory effects of extracts and L-citrulline were reversed upon the addition of NO inhibitors, and pretreatment of tissues with these inhibitors prevented the actions of both extracts and L-citrulline. Thus, these data show that watermelon and citrulline are potent tocolytics, decreasing the force produced by calcium entry and SR release and arising by different pathways, including oxytocin stimulation. Their major mechanism is to stimulate the NO-cyclic guanosine monophosphate (cGMP) relaxant pathway.
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Affiliation(s)
- Phukphon Munglue
- Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand
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23
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Molecular pathways regulating contractility in rat uterus through late gestation and parturition. Am J Obstet Gynecol 2012; 207:76.e15-24. [PMID: 22727353 DOI: 10.1016/j.ajog.2012.04.036] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 04/18/2012] [Accepted: 04/30/2012] [Indexed: 01/25/2023]
Abstract
OBJECTIVE Endogenous uterine agonists can activate numerous signaling pathways to effect increased force. Our objective was to assess expression of key constituents of these pathways, in alliance with contractile function, through late gestation and during term and preterm labor. STUDY DESIGN Using myography, we measured the response to 3 agonists compared with depolarization alone (K(+), 124 mEq/L) and calculated agonist/depolarization ratio. We measured gene expression using quantitative reverse transcription-polymerase chain reaction. RESULTS Contractile responsiveness to depolarization alone, oxytocin, or endothelin-1 increased during pregnancy compared with nonpregnant animals. The agonist/depolarization ratio did not change during uterine activation or parturition. Inhibition of rhoA-associated kinase decreased responses to oxytocin in all tissues, but significantly more during uterine activation. Expression of rhoA and rhoA-associated kinase was increased significantly in active labor at term or preterm. CONCLUSION The rhoA/rhoA-associated kinase pathway is a key regulator of uterine activation during labor and may be a useful target for the prevention of spontaneous preterm birth.
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Arrowsmith S, Robinson H, Noble K, Wray S. What do we know about what happens to myometrial function as women age? J Muscle Res Cell Motil 2012; 33:209-17. [PMID: 22644420 PMCID: PMC3413813 DOI: 10.1007/s10974-012-9300-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 05/11/2012] [Indexed: 12/12/2022]
Abstract
Much has been written about the effects of aging on reproductive function, especially female fertility. Much less is known about how aging may affect the contractility of the smooth muscle within the uterus, the myometrium. The myometrium is active through a woman’s entire life, not just during pregnancy. Here we will discuss briefly the contractile functions of the uterus and the changes it undergoes throughout the stages of a woman’s life from menstruation and the menopause, before evaluating the evidence for any changes in myometrial contractility and responses as women age, with a particular focus on women of advanced maternal age. We present original contractility analysis for the widest data set for human myometrium so far examined, and determine inherent spontaneous activity as well as responses to depolarisation and stimulation with oxytocin. Our data show that in the non-pregnant state there is a significant decrease in contractility for both spontaneous and depolarised-induced contractions, with age. We suggest that muscle atrophy and down regulation of Ca channels may account for this. Interestingly in pregnant myometrium we found a wide range of contractile ability between women and little evidence for decreased spontaneous activity between the ages of 25–40. Oxytocin responses appear to be more affected by aging, a finding that is consistent with previously reported clinical findings, and may partly be the result of membrane lipids such as cholesterol, increasing as women age. The marked differences between the age-related decline of force beyond age 30 in non-pregnant uterus, and the lack of difference in the pregnant state over this period, shows that the uterus retains its ability to respond to gestational hormones. The growth of the pregnant uterus and increase in content of myofibrillar proteins, may abolish any previous age-related force deficit. This finding is consistent with what is apparent for postmenopausal women in their 50s and 60s; that with the appropriate hormonal stimulation the uterus can allow an embryo to implant, and then without further intervention, carry the foetus to term. It is tempting therefore to speculate that unlike other well documented declines in female reproductive functions with age, the myometrium remains able to function into a woman’s 7th decade.
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Affiliation(s)
- Sarah Arrowsmith
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
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25
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Abstract
Myometrial smooth muscle contractility is regulated predominantly through the reversible phosphorylation of MYLs (myosin light chains), catalysed by MYLK (MYL kinase) and MYLP (MYL phosphatase) activities. MYLK is activated by Ca2+-calmodulin, and most uterotonic agonists operate through myometrial receptors that increase [Ca2+]i (intracellular Ca2+ concentration). Moreover, there is substantial evidence for Ca2+-independent inhibition of MYLP in smooth muscle, leading to generation of increased MYL phosphorylation and force for a given [Ca2+]i, a phenomenon known as 'Ca2+-sensitization'. ROCK (Rho-associated kinase)-mediated phosphorylation and inhibition of MYLP has been proposed as a mechanism for Ca2+-sensitization in smooth muscle. However, it is unclear to date whether the mechanisms that sensitize the contractile machinery to Ca2+ are important in the myometrium, as they appear to be in vascular and respiratory smooth muscle. In the present paper, we discuss the signalling pathways regulating MYLP activity and the involvement of ROCK in myometrial contractility, and present recent data from our laboratory which support a role for Ca2+-sensitization in human myometrium.
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Arrowsmith S, Quenby S, Weeks A, Burdyga T, Wray S. Poor spontaneous and oxytocin-stimulated contractility in human myometrium from postdates pregnancies. PLoS One 2012; 7:e36787. [PMID: 22590608 PMCID: PMC3349652 DOI: 10.1371/journal.pone.0036787] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 04/11/2012] [Indexed: 11/18/2022] Open
Abstract
Prolongation of pregnancy i.e. going more than 10 days over the estimated due date, complicates up to 10% of all pregnancies and is associated with increased risk to both mother and fetus. Despite the obvious need for contractions of the uterus to end pregnancy, there have been no studies directly examining the role of uterine smooth muscle, myometrium, in the aetiology of prolonged pregnancy. This study tested the hypothesis that the intrinsic contractile characteristics of myometrium taken from women with prolonged pregnancy (>41 weeks and 3 days) was reduced compared to those delivering at term (39–41 weeks). We recruited women undergoing Caesarean Section (CS) delivery either pre-labour (n = 27) or in labour (n = 66) at term or postdates. The contractile ability of the postdates myometrium, whether spontaneous or elicited by oxytocin or high-K solution, was significantly reduced compared to term myometrium. These differences remained when adjusted for parity and other maternal characteristics. The findings remained significant when expressed per cross sectional area. Histological examination revealed no differences between the two groups. The contractile differences were however related to intracellular Ca transients suggesting an effect of [Ca] on reduced force production in the postdates group. In summary, myometrium from prolonged pregnancies contracts poorly in vitro even when stimulated with oxytocin and in active labour. Responses to high K+ and measurements of Ca suggest that alterations in excitation contraction coupling, rather than any histological changes of the myometrium, may underlie the differences between term and postdates myometrium. We show that postdates pregnancy is associated with poor myometrial activity and suggest that this may contribute to increased myometrial quiescence and hence, prolonged gestation.
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Affiliation(s)
- Sarah Arrowsmith
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
| | - Siobhan Quenby
- Clinical Sciences Research Institute, University of Warwick, Warwick, United Kingdom
| | - Andrew Weeks
- Department of Women and Children's Health, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Theodor Burdyga
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Susan Wray
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
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Al-Qahtani S, Heath A, Quenby S, Dawood F, Floyd R, Burdyga T, Wray S. Diabetes is associated with impairment of uterine contractility and high Caesarean section rate. Diabetologia 2012; 55:489-98. [PMID: 22101974 PMCID: PMC3245824 DOI: 10.1007/s00125-011-2371-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 10/13/2011] [Indexed: 01/23/2023]
Abstract
AIMS/HYPOTHESIS The prevalence of births worldwide complicated by diabetes mellitus is increasing. In the UK, for example, <25% of diabetic women have a non-instrumental vaginal delivery. Strikingly, more than half the Caesarean sections (CS) in these patients are non-elective, but the reasons for this are not understood. We have tested the hypothesis that poor myometrial contractility as a consequence of the disease contributes to this high CS rate. METHODS We compared spontaneous, high K depolarisation and oxytocin-induced contractions from diabetic and matched control patients having an elective CS. To investigate the mechanism of any differences we measured intracellular Ca, and performed western blotting and compared the tissues histologically. RESULTS There was significantly decreased contraction amplitude and duration in uteri from diabetic compared with control patients, even when possible confounders such as BMI were analysed. Reduced intracellular calcium signals and expression of calcium entry channels were found in uteruses from diabetic patients, which, along with a reduction in muscle content found on histological examination, could explain the reduced force. Myometrium from diabetic patients was responsive to oxytocin, but still did not reach the levels found in non-diabetic patients. CONCLUSIONS/INTERPRETATIONS These are the first data investigating myometrium in diabetic patients and they support the hypothesis that there is poorer contractility even in the presence of oxytocin. The underlying mechanism is related to reduced Ca channel expression and intracellular calcium signals and a decrease in muscle mass. We conclude that these factors significantly contribute to the increased emergency CS rate in diabetic patients.
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Affiliation(s)
- S. Al-Qahtani
- Department of Molecular and Cellular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX UK
- Department of Physiology, Medical College, Jazan University, Jazan, Kingdom of Saudi Arabia
| | - A. Heath
- Department of Molecular and Cellular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX UK
| | - S. Quenby
- Liverpool Women’s Hospital, University of Liverpool, Liverpool, UK
- Present Address: Clinical Sciences Research Institute, University of Warwick, Coventry, UK
| | - F. Dawood
- Liverpool Women’s Hospital, University of Liverpool, Liverpool, UK
| | - R. Floyd
- Department of Molecular and Cellular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX UK
| | - T. Burdyga
- Department of Molecular and Cellular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX UK
| | - S. Wray
- Department of Molecular and Cellular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX UK
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Aslanidi O, Atia J, Benson A, van den Berg H, Blanks A, Choi C, Gilbert S, Goryanin I, Hayes-Gill B, Holden A, Li P, Norman J, Shmygol A, Simpson N, Taggart M, Tong W, Zhang H. Towards a computational reconstruction of the electrodynamics of premature and full term human labour. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:183-92. [DOI: 10.1016/j.pbiomolbio.2011.07.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 07/05/2011] [Indexed: 01/02/2023]
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Gravina FS, Parkington HC, Kerr KP, de Oliveira RB, Jobling P, Coleman HA, Sandow SL, Davies MM, Imtiaz MS, van Helden DF. Role of mitochondria in contraction and pacemaking in the mouse uterus. Br J Pharmacol 2011; 161:1375-90. [PMID: 20942856 DOI: 10.1111/j.1476-5381.2010.00949.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND AND PURPOSE Uterine spontaneous contraction and pacemaking are poorly understood. This study investigates the role of the mitochondrial Ca(2+) store in uterine activity. EXPERIMENTAL APPROACH We investigated the effects of mitochondrial and sarco-endoplasmic reticulum (SER) inhibitors on contraction, membrane potential (Vm) and cytosolic Ca(2+) concentration ([Ca(2+) ](c) ) in longitudinal smooth muscle of the mouse uterus. KEY RESULTS The mitochondrial agents rotenone, carbonylcyanide-3-chlorophenylhydrazone (CCCP), 7-chloro-5-(2-chlorophenyl)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one (CGP37157) and kaempferol decreased the force of contractions. The ATP synthase inhibitor oligomycin had no significant effect. The effects of these agents were compared with those of SER inhibitors cyclopiazonic acid (CPA), 2-amino ethoxyphenylborate (2-APB) and caffeine. All agents, except CPA and oligomycin, decreased contractile force. CPA and CCCP transiently increased contraction frequency, which returned to control levels, whereas rotenone, CGP37157, kaempferol and 2-APB decreased frequency and caffeine had no significant effect. Application of the mitochondrial agents when CPA functionally inhibited stores did not change contraction frequency but, with the exception of kaempferol, decreased force. CCCP caused depolarization and maintained increase in [Ca(2+) ](c) or depolarization/transient hyperpolarization and transient increase in [Ca(2+) ](c) for oestrus and di-oestrus tissues respectively. Rotenone caused hyperpolarization and maintained increase in [Ca(2+) ](c) . CGP37157 and kaempferol caused hyperpolarization but no measurable change in [Ca(2+) ](c) . Application of a range of K(+) channel blockers indicated a role of Ca(2+) -activated K(+) (K(Ca) ) channels in the CCCP- and CGP37157-induced actions. CONCLUSIONS AND IMPLICATIONS Mitochondria have a modulatory role on uterine contractions, with mitochondrial inhibition reducing contraction amplitude and pacemaker frequency by changes in Vm, [Ca(2+) ](c) and/or Ca(2+) influx.
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Affiliation(s)
- F S Gravina
- School of Biomedical Sciences, University of Newcastle, Callaghan, NSW, Australia
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30
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A Modified Hai–Murphy Model of Uterine Smooth Muscle Contraction. Bull Math Biol 2011; 74:143-58. [DOI: 10.1007/s11538-011-9681-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2011] [Accepted: 07/14/2011] [Indexed: 10/17/2022]
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31
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Lecarpentier ER, Claes VA, Timbely O, Arsalane A, Wipff JA, Hébert JLM, Michel FY, Lecarpentier YC. Mechanics and energetics of myosin molecular motors from nonpregnant human myometrium. J Appl Physiol (1985) 2011; 111:1096-105. [PMID: 21778420 DOI: 10.1152/japplphysiol.00414.2011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mechanical properties of spontaneously contracting isolated nonpregnant human myometrium (NPHM) were investigated throughout the whole continuum of load from zero load up to isometry. This made it possible to assess the three-dimensional tension-velocity-length (T-V-L) relationship characterizing the level of contractility and to determine crossbridge (CB) kinetics of myosin molecular motors. Seventy-seven muscle strips were obtained from hysterectomy in 42 nonpregnant patients. Contraction and relaxation parameters were measured during spontaneous mechanical activity. The isotonic tension-peak velocity (T-V) relationship was hyperbolic in 30 cases and nonhyperbolic in 47 cases. When the T-V relationship was hyperbolic, the Huxley formalism could be used to calculate CB kinetics and CB unitary force. At the whole muscle level and for a given isotonic load level, part of the V-L phase plane showed a common pathway, so that a given instantaneous length corresponded to only one possible instantaneous velocity, independent of time and initial length. At the molecular level, rate constants for CB attachment and detachment were dramatically low, ∼100 times lower than those of striated muscles, and ∼5 to 10 times lower than those of other smooth muscles. The CB unitary force was ∼1.4 ± 0.1 pN. NPHM shared similar basic contractile properties with striated muscles, reflected in the three-dimensional T-V-L relationship characterizing the contractile level. Low CB attachment and detachment rate constants made it possible to generate normal CB unitary force and normal muscle tension in NPHM, even though it contracted extremely slowly compared with other muscles.
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Lijuan W, Kupittayanant P, Chudapongse N, Wray S, Kupittayanant S. The Effects of Wild Ginger (Costus speciosus (Koen) Smith) Rhizome Extract and Diosgenin on Rat Uterine Contractions. Reprod Sci 2011; 18:516-24. [DOI: 10.1177/1933719110391278] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Wanwisa Lijuan
- Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Pakanit Kupittayanant
- Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Nuannoi Chudapongse
- Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Susan Wray
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Sajeera Kupittayanant
- Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand
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Abstract
In this review we overview the mechanisms responsible for uterine contractility and relaxation. We then use this as the basis for discussing the two major uterotonins, oxytocin and prostaglandins followed by currently available (although often unlicensed) tocolytics; progesterone, magnesium, calcium channel blockers, oxytocin receptor blockers, β-adrenergic receptor agonists, prostaglandin synthesis inhibitors and nitric oxide donors. In this brief review we have concentrated on the most important mechanisms of action and data obtained on human tissue. By focussing on mechanisms, meta-analyses and Cochrane literature reviews, our aim is to provide insight for clinical usefulness, and highlight where further research is required and where the targets may be.
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Affiliation(s)
- Sarah Arrowsmith
- is a PhD Student in the Physiological Laboratory at University of Liverpool, Liverpool, UK. Conflicts of interest: none declared
| | - Annabelle Kendrick
- is a PhD Student in the Physiological Laboratory at University of Liverpool, Liverpool, UK. Conflicts of interest: none declared
| | - Susan Wray
- is a PhD Student in the Physiological Laboratory at University of Liverpool, Liverpool, UK. Conflicts of interest: none declared
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Abstract
The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a "one model fits all" approach to this subject, we have tried to synthesize conclusions wherever possible.
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Affiliation(s)
- Susan Wray
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Liverpool, Merseyside L69 3BX, United Kingdom.
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Promprom W, Kupittayanant P, Indrapichate K, Wray S, Kupittayanant S. The Effects of Pomegranate Seed Extract and β-Sitosterol on Rat Uterine Contractions. Reprod Sci 2009; 17:288-96. [DOI: 10.1177/1933719109352687] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Wilawan Promprom
- Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Pakanit Kupittayanant
- Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Korakod Indrapichate
- Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Susan Wray
- The Physiological Laboratories, School of Biomedical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Sajeera Kupittayanant
- Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand,
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36
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Turton P, Neilson JP, Quenby S, Burdyga T, Wray S. A short review of twin pregnancy and how oxytocin receptor expression may differ in multiple pregnancy. Eur J Obstet Gynecol Reprod Biol 2009; 144 Suppl 1:S40-4. [DOI: 10.1016/j.ejogrb.2009.02.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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37
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Burdyga T, Borisova L, Burdyga AT, Wray S. Temporal and spatial variations in spontaneous Ca events and mechanical activity in pregnant rat myometrium. Eur J Obstet Gynecol Reprod Biol 2009; 144 Suppl 1:S25-32. [PMID: 19282086 DOI: 10.1016/j.ejogrb.2009.02.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
OBJECTIVES The aim of this study was to investigate the temporal and spatial characteristics of spontaneous Ca signals in pregnant rat myometrium. STUDY DESIGN Confocal imaging of longitudinal strips of 21-day pregnant rats loaded with the Ca sensitive indicator Fluo-4, was combined with measurements of mechanical activity in uterine smooth muscle cells, in situ and freshly isolated. RESULTS Our results show that the Ca transients in pregnant uterine tissue are composed of Ca spikes, which are associated with the spike-like action potentials. There is large variation in the pattern of spontaneous activity in myometrium, ranging from non-propagating Ca spikes confined to individual smooth muscle cells, through to regional and global propagating Ca spikes. Irrespective of the pattern of activity displayed, the Ca signals were always in the form of Ca spikes, singularly or in bursts. These Ca spikes did not show fixed initiations sites, propagated in longitudinal and transverse directions from the initiation regions, and had a variable pattern of propagation in preparations which were not synchronously active. In preparations which showed synchronous activity, Ca spikes singularly or bursts propagated mainly in the transverse direction from the initiation regions. The amplitude of force generated by single spikes was dependent on the number of bundles recruited by the propagating Ca spike within the strip, and was about 30-40% of the maximal force produced by carbachol or high-K stimulation. If Ca spikes appeared in the form of bursts they generated longer lasting fused contractions, the amplitudes of which were dependent on the number and the frequency of Ca spikes in the burst. CONCLUSIONS Longitudinal myometrium from pregnant rats generates spontaneous Ca spikes which vary in their initiation sites, spatial spread and frequency and are associated with the spike-like action potentials. They are sensitive to the L-type Ca channel blocker, nifedipine. Contractile activity was dependent on the spatial spread of individual Ca spikes and when fully synchronized, produced single submaximal phasic contraction. The number and frequency of bursts of Ca spikes controlled the amplitude and duration of contraction.
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Affiliation(s)
- Theodor Burdyga
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L693BX, UK.
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38
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Noble K, Matthew A, Burdyga T, Wray S. A review of recent insights into the role of the sarcoplasmic reticulum and Ca entry in uterine smooth muscle. Eur J Obstet Gynecol Reprod Biol 2009; 144 Suppl 1:S11-9. [PMID: 19285773 DOI: 10.1016/j.ejogrb.2009.02.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The uterine sacroplasmic reticulum (SR) takes up and stores calcium [Ca], using an ATPase (SERCA) and the Ca-buffering proteins, calsequestrin and calreticulin. This stored Ca can be released via IP(3)-gated Ca channels. Decreases in luminal Ca concentration [Ca] have been directly measured following agonist stimulation. During spontaneous contractions however, there appears to be no involvement of the SR, as Ca entry and efflux across the plasma membrane account for these phasic contractions. After over-viewing current knowledge concerning SR structure and function, we highlight three areas of research which suggest new ways of looking at the role of the SR in the uterus, although they may be controversial or speculative at the moment. Firstly, we review the evidence for the function, if any, of Ca-induced SR Ca release channels, the ryanodine receptor (RyR) and the lack of Ca sparks (the elemental release events from RyRs), in the uterus. Secondly, we ask does regulation of SERCA by the accessory protein, phospholamban, occur in the uterus and what is the effect of knocking out phospholamban on uterine activity? Thirdly, we address the question of when and how store-operated Ca entry occurs in the myometrium. By analogy with other, usually less excitable tissues, is there a mechanism that links store Ca depletion to plasma membrane Ca entry in smooth muscle cells within intact uterus and is it physiologically relevant and regulated? Are the recently described proteins ORAI and STIM-1 involved in uterine store-operated Ca entry? We end the review by integrating these new insights with previous data to present a new working model of the SR in the uterus.
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Affiliation(s)
- Karen Noble
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L693BX, UK
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39
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Thaina P, Tungcharoen P, Wongnawa M, Reanmongkol W, Subhadhirasakul S. Uterine relaxant effects of Curcuma aeruginosa Roxb. rhizome extracts. JOURNAL OF ETHNOPHARMACOLOGY 2009; 121:433-443. [PMID: 19026735 DOI: 10.1016/j.jep.2008.10.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Revised: 09/28/2008] [Accepted: 10/08/2008] [Indexed: 05/27/2023]
Abstract
The effects and plausible mechanism of action of Curcuma aeruginosa Roxb. (Zingiberaceae) rhizome chloroform and methanol extracts on the uterine contraction were investigated using isolated uterus strips from estrogen primed rats. The contractile responses were recorded isometrically with a Grass FT03 force transducer connected to a MacLab system. The experiments were carried out on both nonstimulated, agonist- and KCl-stimulated uteri. In the nonstimulated uterus, the two extracts (10-400 microg/ml) had no significant effect. In contrast, in the stimulated uterus, the chloroform and methanol extracts exerted concentration-dependent inhibition of the contractions induced by oxytocin (1 mU/ml), prostaglandin F2alpha (PGF2alpha, 0.5 microg/ml), ACh (3x10(-6) M) and KCl (40 mM) with the IC50 (inhibition of force) of 31.4, 58.59, 56.21 and 29.28 microg/ml; and 57.79, 69.3, 223.8 and 69.19 microg/ml, respectively. Verapamil, the reference L-type calcium channel blocker, exhibited a similar pattern of inhibition with the IC50 of 0.03, 0.25, 0.35 and 0.04 microg/ml. The IC50 of diclofenac against a PGF2alpha-induced contraction was 31.36 microg/ml. It is known that the contraction induced by agonists and KCl is mainly due to calcium influx through the voltage-gated L-type calcium channels opened indirectly or directly by agonist-receptor activation and KCl. Thus, it is speculated that the two plant extracts might inhibit uterine contraction by interrupting the influx of Ca2+ probably through voltage-gated L-type calcium channels. This possibility was further substantiated by the ability of the extracts to shift the CaCl2-contraction curves to the right. As the methanol extract also reduced the contraction of oxytocin in Ca2+-free EDTA solution; thus, it is suggested that part of its action may be involved with an intracellular mechanism. The effect of the two extracts did not involve the activation of beta2-adrenoceptors since their effects were unaffected by propranolol. Based on the inhibitory effect of the extracts on the oxytocin-induced contraction, it is concluded that the extracts might be useful as tocolytic agents for the prevention of preterm labor. Their effects on the inhibition of PGF2alpha-induced contractions also seem useful for the treatment of dysmenorrhea. There are reports by others that the plant rhizome contains beta-pinene and sesquiterpenes. In addition, there is evidence that these compounds possess spasmolytic effects in the rat intestine and uterus. Therefore, the uterine relaxant effect of the plant extracts could be due to beta-pinene and some sesquiterpene lactones contents. The methanol extract is less potent than the chloroform extract, and this might be due to the lower amount of terpene compounds or different compounds may involve in this action.
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Affiliation(s)
- Peerarat Thaina
- Department of Pharmacology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
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40
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Abstract
Smooth muscle cell (SMC) contraction is controlled by the Ca2+ and Rho kinase signalling pathways. While the SMC Rho kinase system seems to be reasonably constant, there is enormous variation with regard to the mechanisms responsible for generating Ca2+ signals. One way of dealing with this diversity is to consider how this system has been adapted to control different SMC functions. Phasic SMCs (vas deferens, uterus and bladder) rely on membrane depolarization to drive Ca2+ influx across the plasma membrane. This depolarization can be induced by neurotransmitters or through the operation of a membrane oscillator. Many tonic SMCs (vascular, airway and corpus cavernosum) are driven by a cytosolic Ca2+ oscillator that generates periodic pulses of Ca2+. A similar oscillator is present in pacemaker cells such as the interstitial cells of Cajal (ICCs) and atypical SMCs that control other tonic SMCs (gastrointestinal, urethra, ureter). The changes in membrane potential induced by these cytosolic oscillators does not drive contraction directly but it functions to couple together individual oscillators to provide the synchronization that is a characteristic feature of many tonic SMCs.
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41
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Wray S, Burdyga T, Noble K. Calcium signalling in smooth muscle. Cell Calcium 2008; 38:397-407. [PMID: 16137762 DOI: 10.1016/j.ceca.2005.06.018] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/28/2005] [Indexed: 11/26/2022]
Abstract
Calcium signalling in smooth muscles is complex, but our understanding of it has increased markedly in recent years. Thus, progress has been made in relating global Ca2+ signals to changes in force in smooth muscles and understanding the biochemical and molecular mechanisms involved in Ca2+ sensitization, i.e. altering the relation between Ca2+ and force. Attention is now focussed more on the role of the internal Ca2+ store, the sarcoplasmic reticulum (SR), global Ca2+ signals and control of excitability. Modern imaging techniques have shown the elaborate SR network in smooth muscles, along with the expression of IP3 and ryanodine receptors. The role and cross-talk between these two Ca(2+) release mechanisms, as well as possible compartmentalization of the SR Ca2+ store are discussed. The close proximity between SR and surface membrane has long been known but the details of this special region to Ca2+ signalling and the role of local sub-membrane Ca2+ concentrations and membrane microdomains are only now emerging. The activation of K+ and Cl- channels by local Ca2+ signals, can have profound effects on excitability and hence contraction. We examine the evidence for both Ca2+ sparks and puffs in controlling ion channel activity, as well as a fundamental role for Ca2+ sparks in governing the period of inexcitability in smooth muscle, i.e. the refractory period. Finally, the relation between different Ca2+ signals, e.g. sparks, waves and transients, to smooth muscle activity in health and disease is becoming clearer and will be discussed.
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Affiliation(s)
- Susan Wray
- Department of Physiology, The University of Liverpool, Liverpool L69 3BX, UK.
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42
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Wray S, Noble K. Sex hormones and excitation-contraction coupling in the uterus: the effects of oestrous and hormones. J Neuroendocrinol 2008; 20:451-61. [PMID: 18266942 DOI: 10.1111/j.1365-2826.2008.01665.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this review, we examine how far the increased understanding that we have of the events in excitation contraction can explain the effects of the oestrous cycle and sex hormones on uterine function. Observational studies of electrical and mechanical activity in the rat myometrium have shown a relative quiescence during pro-oestrous, with little propagation of any electrical events. Thus, uterine activity can be said to approximately inversely reflect plasma 17beta-oestradiol concentrations. We show that Ca(2+) signalling and mechanical activity are greatest in metoestrous and dioestrous compared to pro-oestrous and oestrous. These data are discussed in terms of hormonal effects on Ca(2+) and K(+) channels. Finally, the influence of sex hormones on lipid rafts and caveolae are considered and discussed in relation to recent findings on their role in uterine signalling and contractility, and cholesterol levels and obesity.
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Affiliation(s)
- S Wray
- The Physiological Department, School of Biomedical Sciences, University of Liverpool, Liverpool, UK.
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43
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Abstract
A better understanding of the mechanisms that generate and modulate uterine contractility is needed if progress is to be made in the prevention or treatment of problems in labour. Dysfunctional labour describes the condition when uterine contractility is too poor to dilate the cervix, and it is the leading cause of emergency Caesarean sections. Recently, insight has been gained into a possible causal mechanism for dysfunctional labour. Study of the physiological mechanisms that produce excitation in the uterus, the subsequent Ca(2)(+) signals and biochemical pathway leading to contraction has underpinned this progress. In this review, I give an account of excitation-contraction signalling in the myometrium and explore the implications of recent findings concerning lipid rafts for these processes. I also discuss how changes of pH are fundamentally enmeshed in uterine activity and biochemistry and explore the effect that pH changes will have on human myometrium. Finally, I present the evidence that acidification of the myometrium is correlated with dysfunctional labour and suggest the processes by which it is occurring. It is only by gaining a better understanding of uterine physiology and pathophysiology that progress will be made and research findings translated into clinical benefit for women and their families.
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Affiliation(s)
- Susan Wray
- Department of Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
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44
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Wray S, Shmygol A. Role of the calcium store in uterine contractility. Semin Cell Dev Biol 2007; 18:315-20. [PMID: 17601757 DOI: 10.1016/j.semcdb.2007.05.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Accepted: 05/03/2007] [Indexed: 11/19/2022]
Abstract
This article assesses the nature of the sarcoplasmic reticulum (SR) in uterine smooth muscle. Modern imagining techniques have revealed new information about the location and density of Ca storage and release. Release mechanisms, including IP(3) and Ca itself, via ryanodine receptors (RyR), as well as possible roles for cyclic ADP ribose, and the contribution of the SR to relaxation are detailed. The role of the SR Ca-ATPase in both decay of the Ca transient and maintaining Ca homeostasis is reviewed. Recent data on the role of local Ca signals from the SR in contributing to membrane excitability and contractility are discussed, along with interactions with ion channels in lipid microdomains.
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Affiliation(s)
- Susan Wray
- University of Liverpool, Department of Physiology, Crown Street, Liverpool L69 3BX, United Kingdom.
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45
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Hotta S, Morimura K, Ohya S, Muraki K, Takeshima H, Imaizumi Y. Ryanodine receptor type 2 deficiency changes excitation-contraction coupling and membrane potential in urinary bladder smooth muscle. J Physiol 2007; 582:489-506. [PMID: 17363382 PMCID: PMC2075324 DOI: 10.1113/jphysiol.2007.130302] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The possibility that the ryanodine receptor type 2 (RyR2) can function as the major Ca(2+)-induced Ca(2+) release (CICR) channel in excitation-contraction (E-C) coupling was examined in smooth muscle cells (SMCs) isolated from urinary bladder (UB) of RyR2 heterozygous KO mice (RyR2+/-). RyR2 mRNA expression in UB from RyR2+/- was much lower than that in wild-type (RyR2+/+. In single UBSMCs from RyR2+/+, membrane depolarization under voltage clamp initially induced several local Ca(2+) transients (hot spots) in peripheral areas of the cell. Then, Ca(2+) waves spread from Ca(2+) hot spots to other areas of the myocyte. The number of Ca(2+) hot spots elicited by a short depolarization (< 20 ms) in UBSMCs of RyR2+/- was significantly smaller than in those of RyR2+/+. The force development induced either by direct electrical stimulation or by 10 microm acetylcholine in tissue segments of RyR2+/- was smaller than and comparable to those in RyR2+/+, respectively. The frequency of spontaneous transient outward currents in single myocytes and the membrane depolarization by 1 microm paxilline in tissue segments from RyR2+/- were significantly lower and smaller than those in RyR2+/+, respectively. The urination frequency and volume per voiding in RyR2+/- were significantly increased and reduced, respectively, compared with RyR2+/+. In conclusion, RyR2 plays a crucial role in the regulation of CICR during E-C coupling and also in the regulation of resting membrane potential, presumably via the modulation of Ca(2+)-dependent K(+) channel activity in UBSMCs and, thereby, has a pivotal role in the control of bladder activity.
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Affiliation(s)
- Shingo Hotta
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Science, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
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46
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Burdyga T, Wray S, Noble K. In Situ Calcium Signaling: No Calcium Sparks Detected in Rat Myometrium. Ann N Y Acad Sci 2007; 1101:85-96. [PMID: 17303831 DOI: 10.1196/annals.1389.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Controlled uterine smooth muscle activity is essential for our reproductive health. While we understand reasonably well the steps that produce contraction following a rise in intracellular [Ca], the mechanism controlling excitability and thus the rise of Ca, is less well understood. Here we examine the role of the internal Ca sore, the sarcoplasmic reticulum (SR), and its relation to surface membrane ion channels. We show that despite having a well-developed SR, the rat uterus does not produce the elemental and local Ca signals, known as Ca sparks. This in turn has consequences for excitability, as the negative feedback loop between these Ca signals and Ca-activated K (BK) channels on the surface membrane is lost. This may be important for producing the powerful long-lasting contractions of the uterus required during labor.
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Affiliation(s)
- Theodor Burdyga
- Department of Physiology, The University of Liverpool, Crown Street, Liverpool, L69 3BX, UK.
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Abstract
Existing models of uterine contractions assumed a top-down approach in which the function at the organ or tissue level was explained by the behavior of smaller basic units. A new model of the excitation-contraction process in a single myometrial myocyte was recently developed. This model may be used in a bottom-up approach for the description of the contribution of cellular phenomena to the overall performance of the tissue or organ. In this review, we briefly survey current knowledge of uterine electrophysiology and contractility as well as current modeling techniques, which were successfully used to study the function of various types of muscle cells. In the physiological part of the review, we relate to mechanisms of intracellular Ca(2+) control, Ca(2+) oscillations, and Ca(2+) waves and to the various membranal transport mechanisms regulating ion exchange between the intracellular and extracellular spaces. In addition, we describe the process leading from excitation to contraction. In the modeling part of the review, we present the Hodgkin-Huxley (HH) model of excitation in the squid axon as well as models of Ca(2+) control and the latch-bridge model of Hai and Murphy describing the kinetics of smooth muscle cell (SMC) contraction. We also present integrative models describing more than one of these phenomena. Finally, we suggest how these modeling techniques can be applied to modeling myometrial contraction and thus may significantly contribute to current efforts of research of uterine function.
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Affiliation(s)
- Limor Bursztyn
- Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel.
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Ticconi C, Belmonte A, Piccione E, Rao CHV. Feto-placental communication system with the myometrium inpregnancy and parturition: the role of hormones, neurohormones, inflammatory mediators, and locally active factors. J Matern Fetal Neonatal Med 2006; 19:125-33. [PMID: 16690504 DOI: 10.1080/14767050600555808] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Pregnancy is a unique condition in which the conceptus is allowed to implant, survive, develop, and reach a considerable organ growth and maturation within the maternal body despite the fact that it is half genetically different from the mother. Moreover, it deeply influences the overall endocrine, metabolic, and immunological functions of the recipient mother. These objectives are accomplished through the establishment of several communication systems in which a large array of substances produced by the feto-placental unit reach specific maternal target organs and/or systems and modulate their function. The myometrium is a fundamental reproductive tissue involved in pregnancy maintenance as well as in labor onset and progression and is a potential target organ for such a communication system. An appropriate regulation of myometrial function is a key condition required for pregnancy to develop physiologically until full term is reached and for labor to start. Emerging experimental and clinical evidence suggests that a very complex feto-placental biomolecular communication system exists with the myometrium and is actively operative in the control of myometrial contractility in pregnancy and parturition through the production of a continuously increasing number of substances with endocrine, paracrine, and immunoregulatory actions.
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Affiliation(s)
- Carlo Ticconi
- Department of Surgery, Section of Gynecology and Obstetrics, University of Rome Tor Vergata, Italy.
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Korovkina VP, Brainard AM, England SK. Translocation of an endoproteolytically cleaved maxi-K channel isoform: mechanisms to induce human myometrial cell repolarization. J Physiol 2006; 573:329-41. [PMID: 16527852 PMCID: PMC1779727 DOI: 10.1113/jphysiol.2006.106922] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Large conductance Ca(2+)- and voltage-activated K+ (maxi-K) channels modulate human myometrial smooth muscle cell (hMSMC) excitability; however, the role of individual alternatively spliced isoforms remains unclear. We have previously shown that the transcript of a human maxi-K channel isoform (mK44) is expressed predominantly in myometrial and aortic smooth muscle and forms a functional channel in heterologous expression systems. The mK44 isoform contains unique consensus motifs for both endoproteolytic cleavage and N-myristoylation, although the function of these post-translational modifications is unknown. The goal of these studies was to determine the role of post-translational modifications in regulating mK44 channel function in hMSMCs. An mK44-specific antibody indicated that this channel is localized intracellularly in hMSMCs and translocates to the cell membrane in response to increases in intracellular Ca(2+). Immunological analyses using an N-terminally myc-tagged mK44 construct demonstrated endoproteolytical cleavage of mK44 in hMSMCs resulting in membrane localization of the mK44 N-termini and intracellular retention of the pore-forming C-termini. Caffeine-induced Ca(2+) release from intracellular stores resulted in translocation of the C-termini of mK44 to the cell membrane and co-localization with its N-termini. Translocation of mK44 channels to the cell membrane was concomitant with repolarization of the hMSMCs. Endoproteolytic digest of mK44 did not occur in HEK293 cells or mouse fibroblasts. MK44 truncated at a putative N-myristoylation site did not produce current when expressed alone, but formed a functional channel when co-expressed with the N-terminus. These findings provide novel insight into cell-specific regulation of maxi-K channel function.
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Affiliation(s)
- Victoria P Korovkina
- Department of Physiology and Biophysics, Carver College of Medicine, University of Iowa, 6-432 BSB Iowa City, IA 52242, USA
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Noble K, Zhang J, Wray S. Lipid rafts, the sarcoplasmic reticulum and uterine calcium signalling: an integrated approach. J Physiol 2005; 570:29-35. [PMID: 16239270 PMCID: PMC1464295 DOI: 10.1113/jphysiol.2005.098475] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The pathways involved in Ca2+ signalling in the uterus remain incompletely understood, impairing our ability to prevent preterm and difficult labours. In this review we focus on two elements in the pathway of Ca2+ signalling that have recently emerged as playing important roles: membrane lipid rafts and the sarcoplasmic reticulum. We examine the evidence for lipid rafts in the uterus and discuss their functional role. We suggest that the increases in cytosolic [Ca2+] and contractility that occur with raft disruption are due, at least in part, to effects on large conductance Ca2+-activated K+ (BK) channels that are localized to rafts. The role of the SR in contributing to subsarcolemmal cytosolic microdomains in uterus is evaluated, along with its interactions with ion channels on the plasma membrane. Thus, signalling microdomains play an important, but incompletely understood, role in the uterus, and integrating them into other Ca2+ signalling pathways is a challenge for further research. We suggest that the role of the SR changes in pregnancy, from promoting quiescence via BK channels or SR Ca2+ uptake, to promoting Ca2+ entry and contractility at term, and relate data on lipid rafts to clinical outcome in obese pregnant women.
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Affiliation(s)
- Karen Noble
- Department of Physiology, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
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