Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China.
Department of Biomedicine, Health, Aarhus University, DK-8000 Aarhus C, Denmark.
Int J Mol Sci. 2018 Aug 23;19(9):2489. doi: 10.3390/ijms19092489.
Inhibition of the Na,K-ATPase by ouabain potentiates vascular tone and agonist-induced contraction. These effects of ouabain varies between different reports. In this study, we assessed whether the pro-contractile effect of ouabain changes with arterial diameter and the molecular mechanism behind it. Rat mesenteric small arteries of different diameters (150⁻350 µm) were studied for noradrenaline-induced changes of isometric force and intracellular Ca in smooth muscle cells. These functional changes were correlated to total Src kinase and Src phosphorylation assessed immunohistochemically. High-affinity ouabain-binding sites were semi-quantified with fluorescent ouabain. We found that potentiation of noradrenaline-sensitivity by ouabain correlates positively with an increase in arterial diameter. This was not due to differences in intracellular Ca responses but due to sensitization of smooth muscle cell contractile machinery to Ca. This was associated with ouabain-induced Src activation, which increases with increasing arterial diameter. Total Src expression was similar in arteries of different diameters but the density of high-affinity ouabain binding sites increased with increasing arterial diameters. We suggested that ouabain binding induces more Src kinase activity in mesenteric small arteries with larger diameter leading to enhanced sensitization of the contractile machinery to Ca.
哇巴因抑制 Na,K-ATP 酶可增强血管张力和激动剂诱导的收缩。哇巴因的这些作用在不同的报道中有所不同。在这项研究中，我们评估了哇巴因的促收缩作用是否随动脉直径而变化，以及其背后的分子机制。我们研究了不同直径（150-350 µm）的大鼠肠系膜小动脉，以评估去甲肾上腺素引起的等长力和平滑肌细胞内 Ca 变化。这些功能变化与免疫组织化学评估的总Src 激酶和 Src 磷酸化相关。用荧光哇巴因半定量测定高亲和力哇巴因结合位点。我们发现，哇巴因对去甲肾上腺素敏感性的增强与动脉直径的增加呈正相关。这不是由于细胞内 Ca 反应的差异，而是由于平滑肌细胞收缩机制对 Ca 的敏感性增加。这与哇巴因诱导的Src 激活有关，Src 激活随动脉直径的增加而增加。不同直径的动脉中总 Src 表达相似，但高亲和力哇巴因结合位点的密度随动脉直径的增加而增加。我们认为，哇巴因结合在直径较大的肠系膜小动脉中诱导更多的 Src 激酶活性，从而增强了收缩机制对 Ca 的敏感性。
