Immunohistochemical and functional studies for M3 muscarinic receptors and cyclooxygenase-2 expressed in the mouse atrium.
Immunohistochemical and functional studies for M3 muscarinic receptors and cyclooxygenase-2 expressed in the mouse atrium.
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对小鼠心房中表达的 M3 毒蕈碱受体和环氧合酶 2 进行免疫组织化学和功能研究。
DOI：
10.1111/j.1474-8673.2012.00472.x
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
T.
中科院分区：
文献类型：
--
作者：
Harada;N.;Ochi;K.;Yaosaka;N.;Teraoka;H.;Hiraga;T.;Iwanaga;T.;Unno;T.;Komori;S.;Yamada;M.;Kitazawa;T.
在小鼠心房，M_2和M_3受体（M_2 R和M_3R）参与M_2受体激动剂的双相（负性和正性）变力作用，消炎痛可减弱M_2受体的正性变力作用。本研究的目的是确定M2 R、M3 R和环氧合酶（考克斯）在小鼠心房中的定位，并表征毒蕈碱受体介导的正性肌力作用。在心肌和心内膜内皮中均发现了考克斯-1和考克斯-2免疫反应性。在电刺激左心房时，氨甲酰胆碱引起M2 R介导的负性肌力，然后是M3 R介导的正性肌力。去除心房内皮细胞降低了正性肌力而不影响负性肌力，表明内皮M3 R的刺激介导了正性肌力。（环己氧基）-4-硝基苯基]-甲磺酰胺（NS 398，考克斯-2抑制剂）降低卡巴胆碱诱导的正性肌力;然而，5-（4-氯苯基）-1-（4-甲氧基苯基）-3-三氟甲基吡唑（SC 560，考克斯-1抑制剂），1-[[4，5-双（4-甲氧基苯基）-2-噻唑基]羰基]-4-甲基哌嗪（FR122047，考克斯-1抑制剂）M3受体激活引起右心房自发搏动的正性变时性，M2 R介导的负性变时性受到抑制，收缩率较低，<350次/min。我们的结果表明，尽管M3 R位于心肌细胞和内皮细胞上，但只有内皮M3 R通过激活小鼠心房中的考克斯-2介导对毒蕈碱激动剂的正性变时性。还证实了M3 R介导的正变时性抵消M2 R介导的负变时性。
In mouse atrium, M2and M3muscarinic receptors (M2R and M3R) are involved in biphasic (negative and positive) inotropic actions of muscarinic agonists, and the positive inotropic action is reduced by indomethacin. The aim of our study was to determine the localization of M2R, M3R and cyclo‐oxygenase (COX) in mouse atrium and to characterize muscarinic receptor‐mediated positive inotropy.M2R immunoreactivity was found only on atrial myocardium, but M3R immunoreactivity was localized on both the myocardium and endocardial endothelium. COX‐1 and COX‐2 immunoreactivities were identified in both myocardial and endocardial endothelium.In electrically stimulated left atria, carbachol caused M2R‐mediated negative inotropy followed by M3R‐mediated positive inotropy. Removal of atrial endothelium reduced the positive inotropy without affecting the negative inotropy, suggesting that stimulation of endothelial M3R mediates the positive inotropy.N‐[2‐(cyclohexyloxy)‐4‐nitrophenyl]‐methanesulfonamide (NS398, COX‐2 inhibitor)decreased the carbachol‐induced positive inotropy; however, 5‐(4‐chlorophenyl)‐1‐(4‐methoxyphenyl)‐3‐trifluoromethylpyrazole (SC560, COX‐1 inhibitor), 1‐[[4,5‐bis(4‐methoxyphenyl)‐2‐thiazolyl]carbonyl]‐4‐methylpiperazine (FR122047, COX‐1 inhibitor) andl‐nitroarginine methylester did not affect the inotropic response.M3R activation caused positive chronotropy in spontaneously beating right atria when M2R‐mediated negative chronotropy was suppressed and rate of contraction was low, <350 beats min−1.Our results indicate that although M3Rs are located on both myocardial cells and endocardial endothelial cells, only endothelial M3Rs mediate positive inotropy in response to muscarinic agonists via activation of COX‐2 in the mouse atrium. M3R‐mediated positive chronotropy counteracting M2R‐mediated negative chronotropy was also demonstrated.