Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
Free Radic Biol Med. 2012 Mar 1;52(5):860-70. doi: 10.1016/j.freeradbiomed.2011.11.036. Epub 2011 Dec 23.
Ca(2+)-activated K(+) channels (K(Ca)) and NO play a central role in the endothelium-dependent control of vasomotor tone. We evaluated the interaction of K(Ca) with NO production in isolated arterial mesenteric beds of the rat. In phenylephrine-contracted mesenteries, acetylcholine (ACh)-induced vasodilation was reduced by NO synthase (NOS) inhibition with N(ω)-nitro-L-arginine (L-NA), but in the presence of tetraethylammonium, L-NA did not further affect the response. In KCl-contracted mesenteries, the relaxation elicited by 100 nM ACh or 1 μM ionomycin was abolished by L-NA, tetraethylammonium, or simultaneous blockade of small-conductance K(Ca) (SK(Ca)) channels with apamin and intermediate-conductance K(Ca) (IK(Ca)) channels with triarylmethane-34 (TRAM-34). Apamin-TRAM-34 treatment also abolished 100 nM ACh-activated NO production, which was associated with an increase in superoxide formation. Endothelial cell Ca(2+) buffering with BAPTA elicited a similar increment in superoxide. Apamin-TRAM-34 treatment increased endothelial NOS phosphorylation at threonine 495 (P-eNOS(Thr495)). Blockade of NAD(P)H oxidase with apocynin or superoxide dismutation with PEG-SOD prevented the increment in superoxide and changes in P-eNOS(Thr495) observed during apamin and TRAM-34 application. Our results indicate that blockade of SK(Ca) and IK(Ca) activates NAD(P)H oxidase-dependent superoxide formation, which leads to inhibition of NO release through P-eNOS(Thr495). These findings disclose a novel mechanism involved in the control of NO production.
钙激活钾通道（KCa）和一氧化氮（NO）在血管平滑肌张力的内皮依赖性调节中发挥核心作用。我们评估了 KCa 与大鼠分离肠系膜动脉床中 NO 产生的相互作用。在去甲肾上腺素收缩的肠系膜中，乙酰胆碱（ACh）诱导的血管舒张被 NO 合酶（NOS）抑制剂 Nω-硝基-L-精氨酸（L-NA）抑制，但在四乙铵存在下，L-NA 不再影响反应。在 KCl 收缩的肠系膜中，100 nM ACh 或 1 μM 离子霉素引起的舒张被 L-NA、四乙铵或同时用蜂毒肽和三芳基甲烷-34（TRAM-34）阻断小电导钙激活钾通道（SKCa）和中电导钙激活钾通道（IKCa）所消除。蜂毒肽-TRAM-34 处理还消除了 100 nM ACh 激活的 NO 产生，这与超氧化物形成的增加有关。内皮细胞 Ca2+缓冲用 BAPTA 也引起超氧化物的类似增加。蜂毒肽-TRAM-34 处理增加了内皮型一氧化氮合酶（eNOS）在苏氨酸 495 位的磷酸化（P-eNOS(Thr495)）。apocynin 阻断 NAD(P)H 氧化酶或 PEG-SOD 超氧化物歧化酶阻断超氧化物的增加和在蜂毒肽和 TRAM-34 应用过程中观察到的 P-eNOS(Thr495)的变化。我们的结果表明，SKCa 和 IKCa 的阻断激活了 NAD(P)H 氧化酶依赖性超氧化物的形成，这导致通过 P-eNOS(Thr495)抑制 NO 的释放。这些发现揭示了一种参与控制 NO 产生的新机制。
