Matchkov Vladimir V, Rahman Awahan, Bakker Linda M, Griffith Tudor M, Nilsson Holger, Aalkjaer Christian
The Water and Salt Research Center, Institute of Physiology and Biophysics, University of Aarhus, Aarhus, Denmark.
Am J Physiol Heart Circ Physiol. 2006 Jul;291(1):H357-67. doi: 10.1152/ajpheart.00681.2005. Epub 2006 Jan 20.
Synthetic peptides homologous to the extracellular loops of the major vascular connexins represent a novel class of gap junction blockers that have been used to assess the role of direct cellular communication in arteries and veins. However, the specificity of action of such peptides on the coupling between smooth muscle cells (SMCs) has not yet been fully characterized. Isolated third-order rat mesenteric arteries were therefore studied with respect to isometric tension (myography), intracellular Ca2+ concentration ([Ca2+]i) (Ca2+ -sensitive dyes), membrane potential, and input resistance (sharp intracellular glass electrodes). Confocal imaging was used for visualization of [Ca2+]i events in individual SMCs in the arterial wall and membrane currents (patch clamp) measured in individual SMCs isolated from the same arteries. A triple peptide combination (37,43Gap 27 + 40Gap 27 + 43Gap 26) increased intercellular resistance (measured as input resistance) in intact arterial segments without affecting the membrane conductance of individual cells and also interrupted electrical coupling between pairs of rat aortic A7r5 myocytes. In intact arterial segments, the peptides desynchronized [Ca2+]i transients in individual SMCs and abolished vasomotion without suppressing Ca2+ transients in individual cells. They also depolarized SMCs, increased [Ca2+]i, and attenuated acetylcholine-induced, endothelium-dependent smooth muscle hyperpolarization. Experiments with endothelium-denuded arteries suggested that the depolarization produced by the peptides under basal conditions was in part secondary to electrical uncoupling of the endothelium from SMCs with loss of a tonic hyperpolarizing effect of the endothelium. Taken together, the results indicate that connexin-mimetic peptides block electrical signaling in rat mesenteric small arteries without exerting major nonjunctional effects.
与主要血管连接蛋白细胞外环同源的合成肽代表了一类新型的间隙连接阻滞剂，已被用于评估直接细胞通讯在动脉和静脉中的作用。然而，此类肽对平滑肌细胞（SMC）之间耦合作用的特异性尚未得到充分表征。因此，研究人员使用离体的三级大鼠肠系膜动脉，对其进行等长张力（肌动描记法）、细胞内钙离子浓度（[Ca2+]i）（钙离子敏感染料）、膜电位和输入电阻（尖锐的细胞内玻璃电极）方面的研究。共聚焦成像用于观察动脉壁中单个SMC内的[Ca2+]i事件以及从同一动脉分离出的单个SMC中测量的膜电流（膜片钳）。一种三联肽组合（37,43Gap 27 + 40Gap 27 + 43Gap 26）增加了完整动脉段的细胞间电阻（以输入电阻衡量），而不影响单个细胞的膜电导，并且还中断了大鼠主动脉A7r5心肌细胞对之间的电耦合。在完整的动脉段中，这些肽使单个SMC内的[Ca2+]i瞬变不同步，并消除血管运动，而不抑制单个细胞内的Ca2+瞬变。它们还使SMC去极化，增加[Ca2+]i，并减弱乙酰胆碱诱导的、内皮依赖性的平滑肌超极化。对去内皮动脉的实验表明，在基础条件下肽产生的去极化部分继发于内皮与SMC的电脱耦联，导致内皮的张力性超极化作用丧失。综上所述，结果表明连接蛋白模拟肽可阻断大鼠肠系膜小动脉中的电信号传导，而不产生主要的非连接效应。
