Schwinger R H, Hoischen S, Reuter H, Hullin R
Laboratory of Muscle Research and Molecular Cardiology, Clinic III for Internal Medicine, University of Cologne, Köln, Germany.
J Mol Cell Cardiol. 1999 Jan;31(1):283-96. doi: 10.1006/jmcc.1998.0869.
The purpose of the present study was to investigate the expression and functional relevance of sarcolemmal L-type Ca2+-channels in failing and non-failing human myocardium. The protein expression of sarcolemmal L-type Ca2+-channels was determined with 3H-(+)-PN 200-110-binding experiments and Western blot analysis using a specific antibody against the alpha1-subunit in membrane preparations of ventricular and atrial myocardium from both failing (n = 15) and non-failing hearts (n = 8). The gene expression of the ion conducting pore of the L-type Ca2+-channel was examined with Northern blot technique in human failing and non-failing RNA. For normalization the RNA expression of calsequestrin was used. In electrically driven ventricular papillary muscle strips and auricular trabeculae, the responses to nifedipine and Ca2+ as parameters of myocardial function were studied. The protein expression as measured by 3H-(+)-PN 200-110-binding (Bmax) and Western Blot analysis with calsequestrin as reference was similar in left ventricular failing and non-failing myocardium. However, both were reduced in atrial compared to ventricular tissue in failing and non-failing hearts. The KD remained unchanged. Calsequestrin levels were unaltered in failing and non-failing hearts. The gene expression of the alpha1-subunit was similar in human failing and non-failing hearts. The L-type Ca2+-channel antagonist nifedipine reduced force of contraction with the same potency and efficiency in ventricular failing and non-failing myocardium. In contrast, the potency of nifedipine was higher in atrial than in ventricular tissue. Consistently, atrial myocardium from patients with dilated cardiomyopathy was more sensitive towards Ca2+ than those of the control group. In conclusion, the altered Ca2+-homeostasis in failing human myocardium may be less due to changes in sarcolemmal L-type Ca2+-channel expression or function than due to an altered intracellular Ca2+-handling.
本研究的目的是调查肌膜L型钙通道在衰竭和非衰竭的人心肌中的表达及其功能相关性。采用³H-(+)-PN 200-110结合实验和蛋白质免疫印迹分析，使用针对α1亚基的特异性抗体，测定衰竭（n = 15）和非衰竭心脏（n = 8）的心室和心房心肌膜制剂中肌膜L型钙通道的蛋白质表达。用Northern印迹技术检测人衰竭和非衰竭RNA中L型钙通道离子传导孔的基因表达。以肌集钙蛋白的RNA表达作为标准化对照。在电驱动的心室乳头肌条和心房小梁中，研究硝苯地平和Ca²⁺作为心肌功能参数的反应。通过³H-(+)-PN 200-110结合（Bmax）测量的蛋白质表达以及以肌集钙蛋白为参照的蛋白质免疫印迹分析显示，左心室衰竭和非衰竭心肌中的表达相似。然而，在衰竭和非衰竭心脏中，与心室组织相比，心房中的表达均降低。解离常数（KD）保持不变。衰竭和非衰竭心脏中的肌集钙蛋白水平未改变。α1亚基的基因表达在人衰竭和非衰竭心脏中相似。L型钙通道拮抗剂硝苯地平在心室衰竭和非衰竭心肌中以相同的效力和效率降低收缩力。相比之下，硝苯地平在心房中的效力高于心室组织。同样，扩张型心肌病患者的心房心肌对Ca²⁺比对照组更敏感。总之，衰竭的人心肌中Ca²⁺稳态的改变可能较少归因于肌膜L型钙通道表达或功能的变化，而更多是由于细胞内Ca²⁺处理的改变。
