Cardiovascular & Metabolic Diseases Research Program, Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, 700 George Street, Durham, NC 27707, USA.
J Pharmacol Exp Ther. 2013 Jul;346(1):38-47. doi: 10.1124/jpet.113.205534. Epub 2013 May 2.
Extracellular calcium (Ca²⁺(e))-induced relaxation of isolated, phenylephrine (PE)-contracted mesenteric arteries is dependent on an intact perivascular sensory nerve network that expresses the Ca²⁺-sensing receptor (CaSR). Activation of the receptor stimulates an endocannabinoid vasodilator pathway, which is dependent on cytochrome P450 and phospholipase A₂ but largely independent of the endothelium. In the present study, we determined the role of nitric oxide (NO) in perivascular nerve CaSR-mediated relaxation of PE-contracted mesenteric resistance arteries isolated from mice. Using automated wire myography, we studied the effects of NO synthase (NOS) gene knockout (NOS(-/-)) and pharmacologic inhibition of NOS on Ca²⁺(e)-induced relaxation of PE-contracted arteries. Endothelial NOS knockout (eNOS(-/-)) upregulates but neuronal NOS knockout (nNOS(-/-)) downregulates CaSR expression. NOS(-/-) reduced maximum Ca²⁺(e)-induced relaxation with no change in EC₅₀ values, with eNOS(-/-) having the largest effect. The responses of vessels to calindol and Calhex 231 indicate that the CaSR mediates relaxation. L-N⁵-(1-iminoethyl)-ornithine reduced Ca²⁺(e)-induced relaxation of PE-contracted arteries from C57BL/6 control mice by ≈38% but had a smaller effect in vessels from eNOS(-/-) mice. 7-Nitroindazole had no significant effect on relaxation of arteries from NOS(-/-) mice, but both N(G)-nitro-L-arginine methylester and N(G)-monomethyl-L-arginine significantly reduced the relaxation maxima in all groups. Interestingly, the nNOS-selective inhibitor S-methyl-L-thiocitrulline significantly increased the EC₅₀ value by ≈60% in tissues from C57BL/6 mice but reduced the maximum response by ≈80% in those from nNOS(-/-) mice. Ca²⁺-activated big potassium channels play a major role in the process, as demonstrated by the effect of iberiotoxin. We conclude that CaSR signaling in mesenteric arteries stimulates eNOS and NO production that regulates Ca²⁺(e)-induced relaxation.
细胞外钙 (Ca²⁺(e)) 诱导分离的、苯肾上腺素 (PE) 收缩的肠系膜动脉舒张依赖于完整的血管周围感觉神经网络，该网络表达钙敏感受体 (CaSR)。受体的激活刺激内源性大麻素血管舒张途径，该途径依赖于细胞色素 P450 和磷脂酶 A₂，但在很大程度上独立于内皮细胞。在本研究中，我们确定了一氧化氮 (NO) 在血管周围神经 CaSR 介导的从小鼠分离的 PE 收缩的肠系膜阻力动脉舒张中的作用。使用自动线描记法，我们研究了一氧化氮合酶 (NOS) 基因敲除 (NOS(-/-)) 和 NOS 药理学抑制对 PE 收缩的动脉 Ca²⁺(e) 诱导舒张的影响。内皮型一氧化氮合酶敲除 (eNOS(-/-)) 上调但神经元型一氧化氮合酶敲除 (nNOS(-/-)) 下调 CaSR 表达。NOS(-/-) 降低了最大 Ca²⁺(e) 诱导的舒张，而 EC₅₀ 值没有变化，其中 eNOS(-/-) 的影响最大。Calindol 和 Calhex 231 的反应表明 CaSR 介导舒张。L-N⁵-(1-iminoethyl)-ornithine 降低了来自 C57BL/6 对照小鼠的 PE 收缩的动脉 Ca²⁺(e) 诱导的舒张，而在来自 eNOS(-/-) 小鼠的血管中作用较小。7-硝基吲唑对 NOS(-/-) 小鼠的血管舒张无明显影响，但 N(G)-硝基-L-精氨酸甲酯和 N(G)-单甲基-L-精氨酸均显著降低了所有组的舒张最大值。有趣的是，nNOS 选择性抑制剂 S-甲基-L-硫代瓜氨酸显著增加了来自 C57BL/6 小鼠的组织的 EC₅₀ 值约 60%，但降低了来自 nNOS(-/-) 小鼠的组织的最大反应约 80%。钙激活的大钾通道在该过程中起主要作用，如 iberiotoxin 的作用所示。我们得出结论，肠系膜动脉中的 CaSR 信号刺激 eNOS 和 NO 产生，从而调节 Ca²⁺(e) 诱导的舒张。
