Müller-Ehmsen Jochen, Nickel Johanna, Zobel Carsten, Hirsch Ingo, Bölck Birgit, Brixius Klara, Schwinger Robert H G
Laboratory of Muscle Research and Molecular Cardiology, Department of Internal Medicine III, University of Cologne, Joseph-Stelzmann-Str. 9, 50924 Cologne, Germany.
Basic Res Cardiol. 2003 Mar;98(2):90-6. doi: 10.1007/s00395-003-0396-9.
Cardiac glycosides like ouabain are used in the therapy of heart failure and atrial fibrillation. They exert a positive inotropic effect on cardiomyocytes by inhibiting the plasma membrane sodium pump (Na,K-ATPase), decreasing the Ca-extrusion by the sarcolemmal cardiac sodium/calcium exchanger (NCX) and increasing the intracellular Ca-concentration and Ca-release during subsequent contraction cycles.The longer term effects of ouabain treatment on the expression of proteins important for Ca- and Na-homeostasis are not well known and were investigated in this study. Isolated adult rat cardiomyocytes were cultured in the presence or absence of ouabain (30 microM). In these cells, the expression of the Na,K-ATPase, Na,Ca-exchanger (NCX), the sarcoplasmic reticulum Ca-ATPase (SERCA 2a) and phospholamban (PLB) were studied by Western blot. In addition, the contractile function of these cells was studied after electrical stimulation. After 2 days of ouabain treatment immunoreactivity of the NCX was increased significantly relative to control which was set 1 (1.78 +/- 0.16 vs. 1 +/- 0.13; n = 8; P = 0.003) and at day 4 (1.96 +/- 0.35 vs. 1 +/- 0.20; n = 6; P = 0.02). All other proteins (SERCA 2a, PLB and Na,K-ATPase a1 and b1) remained unchanged (n >/= 4). Ouabain treatment increased the fractional shortening of isolated cardiomyocytes at day 0 (1 Hz: 9.64 +/- 0.73 %, n = 24, vs. 7.18 +/- 0.60 %; n = 21; P = 0.01), whereas at day 2 the contractility was unchanged (1 Hz: 7.23 +/- 1.08 %, n = 9 vs. 7.70 +/- 0.63 %; n = 10, P = 0.71). The inhibition of SERCA 2a (10 microM cyclopiazonic acid (CPA)) decreased contractility in both the ouabain treated group and in controls, at day 0 and at day 2. These results show that chronic ouabain treatment increases the protein expression of the NCX. The positive inotropic effect of ouabain can no longer be observed after a chronic treatment for 2 days. Thus, both protein expression and contractile function of the cells are specifically altered by longer term cardiac glycoside exposure. Whether such regulation can be found in human cardiomyocytes and the resulting consequences in the clinical setting remain to be determined.
像哇巴因这样的强心苷被用于治疗心力衰竭和心房颤动。它们通过抑制质膜钠泵（Na，K - ATP酶）对心肌细胞发挥正性肌力作用，减少肌膜心脏钠/钙交换体（NCX）的钙外流，并在随后的收缩周期中增加细胞内钙浓度和钙释放。哇巴因治疗对钙和钠稳态重要蛋白质表达的长期影响尚不清楚，本研究对此进行了调查。将成年大鼠分离的心肌细胞在有或无哇巴因（30微摩尔）的情况下进行培养。在这些细胞中，通过蛋白质印迹法研究了Na，K - ATP酶、钠钙交换体（NCX）、肌浆网钙ATP酶（SERCA 2a）和受磷蛋白（PLB）的表达。此外，在电刺激后研究了这些细胞的收缩功能。哇巴因处理2天后，NCX的免疫反应性相对于设定为1的对照组显著增加（1.78±0.16对1±0.13；n = 8；P = 0.003），在第4天（1.96±0.35对1±0.20；n = 6；P = 0.02）。所有其他蛋白质（SERCA 2a、PLB以及Na，K - ATP酶a1和b1）保持不变（n≥4）。哇巴因处理在第0天增加了分离心肌细胞的缩短分数（1赫兹：9.64±0.73%，n = 24，对7.18±0.60%；n = 21；P = 0.01），而在第2天收缩性未改变（1赫兹：7.23±1.08%，n = 9对7.70±0.63%；n = 10，P = 0.71）。在第0天和第2天，抑制SERCA 2a（10微摩尔环匹阿尼酸（CPA））降低了哇巴因处理组和对照组的收缩性。这些结果表明，长期哇巴因处理增加了NCX的蛋白质表达。慢性处理2天后不再能观察到哇巴因的正性肌力作用。因此，长期暴露于强心苷会特异性改变细胞的蛋白质表达和收缩功能。这种调节是否能在人类心肌细胞中发现以及在临床环境中的最终后果仍有待确定。
