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The clinical significance of endocardial endothelial dysfunction. Medicina (B Aires) 2017; 53:295-302. [DOI: 10.1016/j.medici.2017.08.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 08/07/2017] [Accepted: 08/29/2017] [Indexed: 01/02/2023] Open
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Wang M, Shibamoto T, Kuda Y, Tanida M, Zhang T, Song J, Kurata Y. The responses of pulmonary and systemic circulation and airway to anaphylactic mediators in anesthetized BALB/c mice. Life Sci 2016; 147:77-84. [DOI: 10.1016/j.lfs.2016.01.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 12/11/2015] [Accepted: 01/21/2016] [Indexed: 11/29/2022]
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Wang M, Shibamoto T, Tanida M, Kuda Y, Kurata Y. Mouse anaphylactic shock is caused by reduced cardiac output, but not by systemic vasodilatation or pulmonary vasoconstriction, via PAF and histamine. Life Sci 2014; 116:98-105. [PMID: 25252221 DOI: 10.1016/j.lfs.2014.09.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 08/27/2014] [Accepted: 09/11/2014] [Indexed: 01/31/2023]
Abstract
AIMS Systemic anaphylaxis is life-threatening, and its pathophysiology is not fully clarified. Mice are frequently used for experimental study on anaphylaxis. However, the hemodynamic features and mechanisms of mouse anaphylactic hypotension remain unknown. Therefore, we determined mechanisms of systemic and pulmonary vascular response to anaphylactic hypotension in anesthetized BALB/c mice by using receptor antagonists of chemical mediators. MAIN METHODS Anaphylaxis was actively induced by an intravenous injection of the ovalbumin antigen into open-chest artificially ventilated sensitized mice. Mean arterial pressure (MAP), pulmonary arterial pressure (PAP), left atrial pressure, central venous pressure, and aortic blood flow (ABF) were continuously measured. KEY FINDINGS In sensitized control mice, MAP and ABF showed initial, transient increases, followed by progressive decreases after the antigen injection. Total peripheral resistance (TPR) did not decrease, while PAP initially and transiently increased to 18.5±0.5mmHg and pulmonary vascular resistance (PVR) also significantly increased. The antigen-induced decreases in MAP and ABF were attenuated by pretreatment with either a platelet-activating factor (PAF) receptor antagonist, CV6209, or a histamine H1 receptor antagonist, diphenhydramine, and were abolished by their combination. Diphenhydramine augmented the initial increases in PAP and PVR, but did not affect the decrease of the corresponding MAP fall. The antagonists of either leukotriene C4 or serotonin, alone or in combination with CV6209, exerted no significant effects. SIGNIFICANCE Mouse anaphylactic hypotension is caused by a decrease in cardiac output but not vasodilatation, via actions of PAF and histamine. The slight increase in PAP is not involved in mouse anaphylactic hypotension.
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Affiliation(s)
- Mofei Wang
- Department of Physiology II, Kanazawa Medical University, Uchinada, Ishikawa 920-0293, Japan; Department of Colorectal Surgery, The Fourth Affiliated Hospital of China Medical University, Shenyang 110032, China
| | - Toshishige Shibamoto
- Department of Physiology II, Kanazawa Medical University, Uchinada, Ishikawa 920-0293, Japan.
| | - Mamoru Tanida
- Department of Physiology II, Kanazawa Medical University, Uchinada, Ishikawa 920-0293, Japan
| | - Yuhichi Kuda
- Department of Physiology II, Kanazawa Medical University, Uchinada, Ishikawa 920-0293, Japan
| | - Yasutaka Kurata
- Department of Physiology II, Kanazawa Medical University, Uchinada, Ishikawa 920-0293, Japan
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Recent insights in the paracrine modulation of cardiomyocyte contractility by cardiac endothelial cells. BIOMED RESEARCH INTERNATIONAL 2014; 2014:923805. [PMID: 24745027 PMCID: PMC3972907 DOI: 10.1155/2014/923805] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 02/13/2014] [Accepted: 02/14/2014] [Indexed: 01/04/2023]
Abstract
The cardiac endothelium is formed by a continuous monolayer of cells that line the cavity of the heart (endocardial endothelial cells (EECs)) and the luminal surface of the myocardial blood vessels (intramyocardial capillary endothelial cells (IMCEs)). EECs and IMCEs can exercise substantial control over the contractility of cardiomyocytes by releasing various factors such as nitric oxide (NO) via a constitutive endothelial NO-synthase (eNOS), endothelin-1, prostaglandins, angiotensin II, peptide growth factors, and neuregulin-1. The purpose of the present paper is actually to shortly review recent new information concerning cardiomyocytes as effectors of endothelium paracrine signaling, focusing particularly on contractile function. The modes of action and the regulatory paracrine role of the main mediators delivered by cardiac endothelial cells upon cardiac contractility identified in cardiomyocytes are complex and not fully described. Thus, careful evaluation of new therapeutic approaches is required targeting important physiological signaling pathways, some of which have been until recently considered as deleterious, like reactive oxygen species. Future works in the field of cardiac endothelial cells and cardiac function will help to better understand the implication of these mediators in cardiac physiopathology.
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An Inotropic Action Caused by Muscarinic Receptor Subtype 3 in Canine Cardiac Purkinje Fibers. ISRN PHARMACOLOGY 2013; 2013:207671. [PMID: 24260719 PMCID: PMC3821913 DOI: 10.1155/2013/207671] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 08/28/2013] [Indexed: 11/18/2022]
Abstract
Objective. The objective of this study was to investigate the inotropic mechanisms and the related muscarinic receptor subtype of acetylcholine (ACh) in canine cardiac Purkinje fibers. Materials and Methods. Isolated Purkinje fiber bundles were used for the measurement of contraction. The receptor subtype was determined using PCR and real-time PCR methods. Results. ACh evoked a biphasic response with a transient negative inotropic effect followed by a positive inotropic effect in a concentration-dependent manner. The biphasic inotropic actions of ACh were inhibited by the pretreatment with atropine. Caffeine inhibited the positive inotropic effect of ACh. ACh increased inositol-1,4,5-trisphosphate content in the Purkinje fibers, which was abolished by atropine. Muscarinic subtypes 2 (M2) and 3 (M3) mRNAs were detected in the canine Purkinje fibers albeit the amount of M3 mRNA was smaller than M2 mRNA. M1 mRNA was not detected. Conclusion. These results suggest that the positive inotropic action of ACh may be mediated by the activation of IP3 receptors through the stimulation of M3 receptors in the canine cardiac Purkinje fibers.
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Harada N, Ochi K, Yaosaka N, Teraoka H, Hiraga T, Iwanaga T, Unno T, Komori S, Yamada M, Kitazawa T. Immunohistochemical and functional studies for M3muscarinic receptors and cyclo-oxygenase-2 expressed in the mouse atrium. ACTA ACUST UNITED AC 2012; 32:41-52. [DOI: 10.1111/j.1474-8673.2012.00472.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Revised: 03/08/2012] [Accepted: 04/15/2012] [Indexed: 11/30/2022]
Affiliation(s)
- N. Harada
- Department of Veterinary Medicine; Rakuno Gakuen University; Ebetsu; Hokkaido; 069-8501; Japan
| | - K. Ochi
- Department of Veterinary Medicine; Rakuno Gakuen University; Ebetsu; Hokkaido; 069-8501; Japan
| | - N. Yaosaka
- Department of Veterinary Science; Rakuno Gakuen University; Ebetsu; Hokkaido; 069-8501; Japan
| | - H. Teraoka
- Department of Veterinary Medicine; Rakuno Gakuen University; Ebetsu; Hokkaido; 069-8501; Japan
| | - T. Hiraga
- Department of Veterinary Medicine; Rakuno Gakuen University; Ebetsu; Hokkaido; 069-8501; Japan
| | - T. Iwanaga
- Department of Functional Morphology, Laboratory of Histology and Cytology; Hokkaido University Graduate School of Medicine; Sapporo; 060-8638; Japan
| | - T. Unno
- Laboratory of Pharmacology, Faculty of Applied Biological Science; Gifu University; Gifu; 501-1193; Japan
| | - S. Komori
- Laboratory of Pharmacology, Faculty of Applied Biological Science; Gifu University; Gifu; 501-1193; Japan
| | - M. Yamada
- Common Resources Group; Okinawa Institute of Science and Technology; Okinawa; 904-0411; Japan
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Hara Y, Ike A, Tanida R, Okada M, Yamawaki H. Involvement of Cyclooxygenase-2 in Carbachol-Induced Positive Inotropic Response in Mouse Isolated Left Atrium. J Pharmacol Exp Ther 2009; 331:808-15. [DOI: 10.1124/jpet.109.156992] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Kitazawa T, Asakawa K, Nakamura T, Teraoka H, Unno T, Komori SI, Yamada M, Wess J. M3 muscarinic receptors mediate positive inotropic responses in mouse atria: a study with muscarinic receptor knockout mice. J Pharmacol Exp Ther 2009; 330:487-93. [PMID: 19429792 DOI: 10.1124/jpet.109.153304] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The potential functional roles of M(3) muscarinic receptors in mouse atria were examined by pharmacological and molecular biological techniques, using wild-type mice, muscarinic M(2) or M(3) receptor single knockout (M(2)KO, M(3)KO), and M(2) and M(3) muscarinic receptor double knockout mice (M(2)/M(3)KO). Real-time quantitative reverse transcriptase-polymerase chain reaction analysis showed that the M(2) receptor mRNA was expressed predominantly in mouse atria but that the M(1), M(3), M(4), and M(5) receptor subtypes were also expressed at low levels. Carbachol (10 nM-30 microM) decreased the spontaneous beating frequency of right atria isolated from wild-type mice. Studies with subtype-preferring antagonists and atria from M(2)KO mice confirmed that this activity is mediated by the M(2) receptor subtype. In left atria from wild-type mice, carbachol decreased the amplitude of electrical field stimulation-evoked contractions (negative inotropic action), but this inhibition was transient and was followed by a gradual increase in contraction amplitude (positive inotropic response). In atria from M(3)KO mice, the transient negative inotropic action of carbachol changed to a sustained negative inotropic action. In contrast, in atria from M(2)KO mice, carbachol showed only positive inotropic activity. In atria from M(2)/M(3) double KO mice, carbachol was devoid of any inotropic activity. These observations, complemented by functional studies with subtype-preferring antagonists, convincingly demonstrate that atrial M(3) muscarinic receptors mediate positive inotropic effects in mouse atria. Physiologically, this activity may serve to dampen the inhibitory effects of M(2) receptor activation on atrial contractility.
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Affiliation(s)
- Takio Kitazawa
- Department of Pharmacology, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
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Namekata I, Fujiki S, Kawakami Y, Moriwaki R, Takeda K, Kawanishi T, Takahara A, Shigenobu K, Tanaka H. Intracellular mechanisms and receptor types for endothelin-1-induced positive and negative inotropy in mouse ventricular myocardium. Naunyn Schmiedebergs Arch Pharmacol 2008; 376:385-95. [PMID: 18172614 DOI: 10.1007/s00210-007-0228-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2007] [Accepted: 11/18/2007] [Indexed: 11/29/2022]
Abstract
We examined the intracellular mechanisms for endothelin-1-induced positive and negative inotropic components that coexist in the mouse ventricular myocardium using isolated ventricular tissue and myocytes from 4-week-old mice. In the presence of SEA0400, a specific inhibitor of the Na+-Ca2+ exchanger, endothelin-1 produced positive inotropy. Endothelin-1, when applied to cardiomyocytes in the presence of SEA0400, did not change the peak amplitude of the Ca2+ transient but increased intracellular pH and Ca2+ sensitivity of contractile proteins. On the other hand, in the presence of dimethylamiloride (DMA), a specific inhibitor of the Na+-H+ exchanger, endothelin-1 produced negative inotropy. In cardiomyocytes, in the presence of DMA, endothelin-1 produced a decrease in peak amplitude of the Ca2+ transient. In the presence of both DMA and SEA0400, endothelin-1 produced neither positive nor negative inotropy. Positive inotropy was blocked by BQ-123 and negative inotropy by BQ-788. These results suggested that endothelin-1-induced positive inotropy is mediated by ET(A) receptors, activation of the Na+-H+ exchanger and an increase in intracellular pH and Ca2+ sensitivity and that the negative inotropy is mediated by ET(B) receptors, activation of the Na+-Ca2+ exchanger and decrease in Ca2+ transient amplitude.
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Affiliation(s)
- Iyuki Namekata
- Department of Pharmacology, Toho University Faculty of Pharmaceutical Sciences, Miyama 2-2-1 Funabashi, Chiba, 274-8510, Japan
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Nishimaru K, Fujiki S, Tanaka Y, Tanaka H, Shigenobu K. Endocardial endothelium-dependent positive inotropy by Ca2+ pump inhibitors: possible involvement of store-operated Ca2+ entry. Pharmacology 2007; 80:200-6. [PMID: 17622753 DOI: 10.1159/000104417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Accepted: 01/24/2007] [Indexed: 11/19/2022]
Abstract
Positive inotropy by sarcoplasmic/endoplasmic reticulum Ca(2+) pump inhibitors was found and its mechanisms were analyzed pharmacologically. Thapsigargin and cyclopiazonic acid produced positive inotropy in isolated mouse left atria. The responses were inhibited by pretreatment of the endocardial surface with Triton X-100 or by indomethacin, which suggests that the inotropic responses were mediated by prostaglandin(s) released from the endocardial endothelium as well as acetylcholine-induced positive inotropy. The thapsigargin- and acetylcholine-induced positive inotropy was significantly inhibited by Gd(3+), La(3+) and lavendustin A, a tyrosine kinase inhibitor, but not by Ni(2+) and LOE908, a non-selective cation channel inhibitor. Gd(3+) and lavendustin A had no effect on the exogenously applied PGF(2)alpha-induced positive inotropy. In addition, acetylcholine did not induce any positive inotropy when applied after the application of thapsigargin. These results strongly suggest that thapsigargin- as well as acetylcholine-induced prostaglandin release from endocardial endothelium is mediated by store-operated Ca(2+) entry through Gd(3+)-sensitive channels and activation of tyrosine kinase.
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Affiliation(s)
- Kazuhide Nishimaru
- Department of Pharmacology, Toho University Faculty of Pharmaceutical Sciences, Funabashi, Chiba, Japan
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Nouchi H, Kaeriyama S, Muramatsu A, Sato M, Hirose K, Shimizu N, Tanaka H, Shigenobu K. Muscarinic receptor subtypes mediating positive and negative inotropy in the developing chick ventricle. J Pharmacol Sci 2007; 103:75-82. [PMID: 17220593 DOI: 10.1254/jphs.fpj06013x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
The inotropic response to muscarinic receptor stimulation of isolated chick ventricular myocardium was examined at various developmental stages, and the receptor subtype involved was pharmacologically characterized. In embryonic chick ventricles, carbachol (CCh) produced positive inotropy at micromolar concentrations. In hatched chick ventricles, CCh produced negative inotropy at nanomolar concentrations. Neither positive nor negative inotropy was observed in the 19 - 21-day-old embryos. Both positive and negative inotropy were also observed with acetylcholine and oxotremoline-M. The CCh-induced positive inotropy in 7 - 9-day-old embryonic ventricles and the negative inotropy in 1 - 3-day-old hatched chick ventricles were antagonized by muscarinic receptor antagonists; pA(2) values for the positive and negative responses of pirenzepine were 7.5 and 7.2, those of AF-DX116 (11-[(2-[(diethylamino)methyl]-1-piperidinyl)acetyl]-5,11-dihydro-6H-pyrido[2,3-b][1,4] benzodiazepine-6-one) were 6.8 and 6.9, those of 4-diphenylacetoxy-N-methylpiperidine (4-DAMP) were 9.0 and 8.5, and those of himbacine were 7.0 and 8.0, respectively. CCh had no effect on action potential configuration. In conclusion, the positive inotropy is most likely mediated by muscarinic M(1) receptors and the negative inotropy is mostly likely mediated by muscarinic M(4) receptors.
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Affiliation(s)
- Hideaki Nouchi
- Department of Pharmacology, Toho University School of Pharmaceutical Sciences, Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan
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Nishimaru K, Tanaka Y, Tanaka H, Shigenobu K. Pharmacological evidence for involvement of phospholipase D, protein kinase C, and sodium-calcium exchanger in alpha-adrenoceptor-mediated negative inotropy in adult mouse ventricle. J Pharmacol Sci 2003; 92:196-202. [PMID: 12890884 DOI: 10.1254/jphs.92.196] [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: 10/27/2022] Open
Abstract
The intracellular signalling pathway for alpha-adrenoceptor-mediated negative inotropy was studied pharmacologically in isolated adult mouse ventricle. The negative inotropy was inhibited by GF-109203X, a nonselective protein kinase C inhibitor. Phorbol 12-myristate 13-acetate also produced sustained negative inotropy, which was inhibited by KB-R7943, a Na(+)/Ca(2+) exchanger inhibitor. The alpha-adrenoceptor-mediated negative inotropy was augmented by RHC-80267, a diacylglycerol lipase inhibitor, but was inhibited either by C(2)-ceramide, a phospholipase D inhibitor, and high concentration of propranolol (50 micro M), which inhibits phosphatidate phosphohydrolase. The inotropy was not affected by U-73122, a phospholipase C inhibitor. Lavendustin-A, a tyrosine kinase inhibitor, also inhibited the negative inotropy. These findings suggest that alpha-adrenoceptor-mediated negative inotropy in adult mouse ventricle is mediated by activation of tyrosine kinase, the phospholipase D-phosphatidate phosphohydrolase pathway, and protein kinase C.
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Affiliation(s)
- Kazuhide Nishimaru
- Department of Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan
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Maier SKG, Westenbroek RE, Yamanushi TT, Dobrzynski H, Boyett MR, Catterall WA, Scheuer T. An unexpected requirement for brain-type sodium channels for control of heart rate in the mouse sinoatrial node. Proc Natl Acad Sci U S A 2003; 100:3507-12. [PMID: 12631690 PMCID: PMC152323 DOI: 10.1073/pnas.2627986100] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated Na(+) channels are composed of pore-forming alpha and auxiliary beta subunits. The majority of Na(+) channels in the heart contain tetrodotoxin (TTX)-insensitive Na(v)1.5 alpha subunits, but TTX-sensitive brain-type Na(+) channel alpha subunits are present and functionally important in the transverse tubules of ventricular myocytes. Sinoatrial (SA) nodal cells were identified in cardiac tissue sections by staining for connexin 43 (which is expressed in atrial tissue but not in SA node), and Na(+) channel localization was analyzed by immunocytochemical staining with subtype-specific antibodies and confocal microscopy. Brain-type TTX-sensitive Na(v)1.1 and Na(v)1.3 alpha subunits and all four beta subunits were present in mouse SA node, but Na(v)1.5 alpha subunits were not. Na(v)1.1 alpha subunits were also present in rat SA node. Isolated mouse hearts were retrogradely perfused in a Langendorff preparation, and electrocardiograms were recorded. Spontaneous heart rate and cycle length were constant, and heart rate variability was small under control conditions. In contrast, in the presence of 100 nM TTX to block TTX-sensitive Na(+) channels specifically, we observed a significant reduction in spontaneous heart rate and markedly greater heart rate variability, similar to sick-sinus syndrome in man. We hypothesize that brain-type Na(+) channels are required because their more positive voltage dependence of inactivation allows them to function at the depolarized membrane potential of SA nodal cells. Our results demonstrate an important contribution of TTX-sensitive brain-type Na(+) channels to SA nodal automaticity in mouse heart and suggest that they may also contribute to SA nodal function and dysfunction in human heart.
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Affiliation(s)
- Sebastian K G Maier
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
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Tanaka H, Nishimaru K, Makuta R, Hirayama W, Kawamura T, Matsuda T, Tanaka Y, Kawanishi T, Shigenobu K. Possible involvement of prostaglandins F(2alpha) and D(2) in acetylcholine-induced positive inotropy in isolated mouse left atria. Pharmacology 2003; 67:157-62. [PMID: 12571412 DOI: 10.1159/000067794] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The inotropic action of prostaglandins PGF(2alpha), PGD(2) and PGE(2) on isolated mouse left atria was characterized and compared with the positive inotropic action of acetylcholine, which has previously been shown to be mediated by prostaglandins released from the endocardial endothelium. PGF(2alpha), PGD(2) and PGE(2) produced positive inotropic responses; the time course of the change in contractile force induced by PGF(2alpha) and PGD(2) was about the same as that by acetylcholine, while that by PGE(2) was slower. Fluprostenol and sulprostone, FP and EP receptor agonists, respectively, had positive inotropic effects while BW-245C, a DP receptor agonist, had no effect. AH-6809, a DP receptor antagonist, had no inhibitory effect on the positive inotropic response to PGD(2). Dimethylamiloride, an inhibitor of Na(+)/H(+) exchange, inhibited the positive inotropic response to PGF(2alpha), PGD(2) and acetylcholine, but not PGE(2). Fluorometric pH measurement with carboxy-SNARF-1-loaded atrial myocytes revealed no change in intracellular pH on application of PGF(2alpha). PGF(2alpha) and PGD(2) significantly prolonged the duration of the atrial action potential while PGE(2) had no significant effect. These findings suggest that prostaglandins induce positive inotropic response in mouse atria through FP and EP receptor stimulation and that the former mechanism mediates in part the positive inotropic response to acetylcholine.
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Affiliation(s)
- Hikaru Tanaka
- Department of Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
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Tanaka H, Kawanishi T, Shigenobu K. Optical Bioimaging: From Living Tissue to a Single Molecule: Atrio-Ventricular Difference in Myocardial Excitation-Contraction Coupling — Sequential Versus Simultaneous Activation of SR Ca2+ Release Units —. J Pharmacol Sci 2003; 93:248-52. [PMID: 14646240 DOI: 10.1254/jphs.93.248] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Rapid-scanning cofocal microscopy has been applied to the analysis of early phase Ca(2+) transients in ventricular and atrial cardiomyocytes. On electrical stimulation of ventricular myocytes, Ca(2+) concentration begins to rise earliest at the Z-line level and becomes uniform throughout the cytoplasm within about 10 ms after the onset of the action potential; transsarcolemmal Ca(2+) influx triggers Ca(2+) release from release sites on the junctional sarcoplasmic reticulum (SR) coupled to T-tubules at the Z-line throughout the cytoplasm. In atrial myocytes lacking the T-tubular network, transsarcolemmal Ca(2+) influx during an action potential triggers SR Ca(2+) release only at subsarcolemmal region. SR Ca(2+) release then spreads towards the central region of the cell through a propagated Ca(2+)-induced-Ca(2+) release mechanism. The atrio-ventricular difference in excitation-contraction coupling mechanisms underlies some of the atrio-ventricular difference in response to physiological and pharmacological stimuli.
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Affiliation(s)
- Hikaru Tanaka
- Department of Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
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Nasuhoglu C, Feng S, Mao Y, Shammat I, Yamamato M, Earnest S, Lemmon M, Hilgemann DW. Modulation of cardiac PIP2 by cardioactive hormones and other physiologically relevant interventions. Am J Physiol Cell Physiol 2002; 283:C223-34. [PMID: 12055091 DOI: 10.1152/ajpcell.00486.2001] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP2) affects profoundly several cardiac ion channels and transporters, and studies of PIP2-sensitive currents in excised patches suggest that PIP2 can be synthesized and broken down within 30 s. To test when, and if, total phosphatidylinositol 4-phosphate (PIP) and PIP(2) levels actually change in intact heart, we used a new, nonradioactive HPLC method to quantify anionic phospholipids. Total PIP and PIP2 levels (10-30 micromol/kg wet weight) do not change, or even increase, with activation of Galpha(q)/phospholipase C (PLC)-dependent pathways by carbachol (50 microM), phenylephrine (50 microM), and endothelin-1 (0.3 microM). Adenosine (0.2 mM) and phorbol 12-myristate 13-acetate (1microM) both cause 30% reduction of PIP2 in ventricles, suggesting that diacylglycerol (DAG)-dependent mechanisms negatively regulate cardiac PIP2. PIP2, but not PIP, increases reversibly by 30% during electrical stimulation (2 Hz for 5 min) in guinea pig left atria; the increase is blocked by nickel (2 mM). Both PIP and PIP2 increase within 3 min in hypertonic solutions, roughly in proportion to osmolarity, and similar effects occur in multiple cell lines. Inhibitors of several volume-sensitive signaling mechanisms do not affect these responses, suggesting that PIP2 metabolism might be sensitive to membrane tension, per se.
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Affiliation(s)
- Cem Nasuhoglu
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA
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