Bridges Lakeesha E, Williams Cicely L, Pointer Mildred A, Awumey Emmanuel M
Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA.
J Vis Exp. 2011 Sep 22(55):3119. doi: 10.3791/3119.
Proximal resistance vessels, such as the mesenteric arteries, contribute substantially to the peripheral resistance. These small vessels of between 100-400 μm in diameter function primarily in directing blood flow to various organs according to the overall requirements of the body. The rat mesenteric artery has a diameter greater than 100 μm. The myography technique, first described by Mulvay and Halpern(1), was based on the method proposed by Bevan and Osher(2). The technique provides information about small vessels under isometric conditions, where substantial shortening of the muscle preparation is prevented. Since force production and sensitivity of vessels to different agonists is dependent on the extent of stretch, according to active tension-length relation, it is essential to conduct contraction studies under isometric conditions to prevent compliance of the mounting wires. Stainless steel wires are preferred to tungsten wires because of oxidation of the latter, which affects recorded responses(3).The technique allows for the comparison of agonist-induced contractions of mounted vessels to obtain evidence for normal function of vascular smooth muscle cell receptors. We have shown in several studies that isolated mesenteric arteries that are contracted with phenylyephrine relax upon addition of cumulative concentrations of extracellular calcium (Ca(2+)(e;)). The findings led us to conclude that perivascular sensory nerves, which express the G protein-coupled Ca(2+)-sensing receptor (CaR), mediate this vasorelaxation response. Using an automated wire myography method, we show here that mesenteric arteries from Wistar, Dahl salt-sensitive(DS) and Dahl salt-resistant (DR) rats respond differently to Ca(2+)(e;). Tissues from Wistar rats showed higher Ca(2+)-sensitivity compared to those from DR and DS. Reduced CaR expression in mesenteric arteries from DS rats correlates with reduced Ca(2+)(e;)-induced relaxation of isolated, pre-contracted arteries. The data suggest that the CaR is required for relaxation of mesenteric arteries under increased adrenergic tone, as occurs in hypertension, and indicate an inherent defect in the CaR signaling pathway in Dahl animals, which is much more severe in DS. The method is useful in determining vascular reactivity ex vivo in mesenteric resistance arteries and similar small blood vessels and comparisons between different agonists and/or antagonists can be easily and consistently assessed side-by-side(6,7,8).
近端阻力血管，如肠系膜动脉，对周围阻力有很大贡献。这些直径在100 - 400μm之间的小血管主要根据身体的总体需求引导血液流向各个器官。大鼠肠系膜动脉的直径大于100μm。肌动描记术由Mulvay和Halpern首次描述(1)，其基于Bevan和Osher提出的方法(2)。该技术可在等长条件下提供有关小血管的信息，在这种条件下可防止肌肉标本大幅缩短。由于根据主动张力 - 长度关系，血管产生的力和对不同激动剂的敏感性取决于拉伸程度，因此在等长条件下进行收缩研究以防止固定线的顺应性至关重要。由于钨丝会氧化，影响记录的反应(3)，所以不锈钢丝比钨丝更受青睐。该技术可比较固定血管对激动剂诱导的收缩情况，以获取血管平滑肌细胞受体正常功能的证据。我们在多项研究中表明，用去氧肾上腺素收缩的离体肠系膜动脉在添加累积浓度的细胞外钙（Ca(2+)(e)）后会舒张。这些发现使我们得出结论，表达G蛋白偶联钙敏感受体（CaR）的血管周围感觉神经介导了这种血管舒张反应。使用自动线肌动描记法，我们在此表明来自Wistar、Dahl盐敏感（DS）和Dahl盐抵抗（DR）大鼠的肠系膜动脉对Ca(2+)(e)的反应不同。与DR和DS大鼠的组织相比，Wistar大鼠的组织显示出更高的钙敏感性。DS大鼠肠系膜动脉中CaR表达的降低与离体预收缩动脉中Ca(2+)(e)诱导的舒张减少相关。数据表明，在高血压等肾上腺素能张力增加的情况下，肠系膜动脉舒张需要CaR，并且表明Dahl动物的CaR信号通路存在内在缺陷，在DS大鼠中更为严重。该方法有助于在离体状态下测定肠系膜阻力动脉及类似小血管的血管反应性，并且可以轻松且一致地同时评估不同激动剂和/或拮抗剂之间的差异(6,7,8)。
