Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Wilhelm Meyers Allé 4, DK-8000 Aarhus C, Denmark.
BESICoS group, Aragón Institute of Engineering Research, IIS-Aragón, University of Zaragoza, 50009 Zaragoza, Spain.
Int J Mol Sci. 2019 Apr 25;20(8):2032. doi: 10.3390/ijms20082032.
We investigated whether the substrate for nitric oxide (NO) production, extracellular l-arginine, contributes to relaxations induced by activating small (SKCa) conductance Ca-activated potassium channels. In endothelial cells, acetylcholine increased H-l-arginine uptake, while blocking the SKCa and the intermediate (IKCa) conductance Ca-activated potassium channels reduced l-arginine uptake. A blocker of the y+ transporter system, l-lysine also blocked H-l-arginine uptake. Immunostaining showed co-localization of endothelial NO synthase (eNOS), SKCa3, and the cationic amino acid transporter (CAT-1) protein of the y+ transporter system in the endothelium. An opener of SKCa channels, cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA) induced large currents in endothelial cells, and concentration-dependently relaxed porcine retinal arterioles. In the presence of l-arginine, concentration-response curves for CyPPA were leftward shifted, an effect unaltered in the presence of low sodium, but blocked by l-lysine in the retinal arterioles. Our findings suggest that SKCa channel activity regulates l-arginine uptake through the y+ transporter system, and we propose that in vasculature affected by endothelial dysfunction, l-arginine administration requires the targeting of additional mechanisms such as SKCa channels to restore endothelium-dependent vasodilatation.
我们研究了一氧化氮（NO）产生的底物，细胞外 l-精氨酸，是否有助于激活小电导钙激活钾通道（SKCa）引起的松弛。在内皮细胞中，乙酰胆碱增加了 H-l-精氨酸的摄取，而阻断 SKCa 和中间电导钙激活钾通道（IKCa）则减少了 l-精氨酸的摄取。y+转运体系统的抑制剂 l-赖氨酸也阻断了 H-l-精氨酸的摄取。免疫染色显示内皮型一氧化氮合酶（eNOS）、SKCa3 和 y+转运体系统的阳离子氨基酸转运蛋白（CAT-1）在内皮细胞中共定位。SKCa 通道的开放剂环己基-[2-（3,5-二甲基吡唑-1-基）-6-甲基嘧啶-4-基]-胺（CyPPA）在内皮细胞中诱导产生大电流，并浓度依赖性地松弛猪视网膜小动脉。在存在 l-精氨酸的情况下，CyPPA 的浓度-反应曲线向左移位，这一效应在低钠存在下不变，但在视网膜小动脉中被 l-赖氨酸阻断。我们的发现表明，SKCa 通道活性通过 y+转运体系统调节 l-精氨酸的摄取，我们提出，在受内皮功能障碍影响的血管中，l-精氨酸的给药需要针对其他机制，如 SKCa 通道，以恢复内皮依赖性血管舒张。
