Finkel M S, Patterson R E, Roberts W C, Smith T D, Keiser H R
Department of Medicine, University of Pittsburgh, Pennsylvania 15213.
Am J Cardiol. 1988 Dec 1;62(17):1281-4. doi: 10.1016/0002-9149(88)90274-3.
The number, affinity, pharmacologic specificity and regional distribution of calcium channel binding sites in human hearts obtained at autopsy and open heart surgery were characterized using the radioligand [3H]nitrendipine. Scatchard analyses of saturation data from 6 autopsy hearts revealed a homogeneous distribution of high affinity binding sites (affinity-1 [KD] = 0.44 +/- 0.06, 0.52 +/- 0.07, 0.32 +/- 0.02, 0.30 +/- 0.03, and 0.45 +/- 0.01 nM; binding capacity [Bmax] = 30 +/- 4, 27 +/- 6, 25 +/- 7, 33 +/- 3, and 28 +/- 4 fmol/mg protein in right atrium, right ventricle, left atrium, left ventricle and ventricular septum, respectively). In ligand competition experiments, nifedipine and nitrendipine completely displaced binding with partial displacement by verapamil and 35% enhancement of binding by 10(-5) M diltiazem at 37 degrees. Analyses of right atrial appendages obtained at open heart surgery from 5 coronary artery bypass patients provided similar results (KD = 0.2 +/- 0.03 nM, Bmax = 42 +/- 2 fmol/mg protein). In addition, no significant differences in KD or Bmax were found in 3 hamster hearts assayed at the time of death or up to 18 hours postmortem at either 4 or 25 degrees. In contrast, there was a significant increase in Bmax (110 fmol/mg protein) with no change in KD (0.3 nM) in a myomectomy specimen from a patient with obstructive hypertrophic cardiomyopathy compared with either autopsy or surgical specimens. These studies illustrate the feasibility and potential advantages of studying calcium channels directly in human hearts.
利用放射性配体[3H]尼群地平对尸检及心脏直视手术获取的人心脏中钙通道结合位点的数量、亲和力、药理特异性及区域分布进行了表征。对6个尸检心脏的饱和数据进行Scatchard分析，结果显示高亲和力结合位点分布均匀（亲和力-1[KD]分别为0.44±0.06、0.52±0.07、0.32±0.02、0.30±0.03和0.45±0.01 nM；结合容量[Bmax]分别为右心房30±4、右心室27±6、左心房25±7、左心室33±3和室间隔28±4 fmol/mg蛋白质）。在配体竞争实验中，硝苯地平和尼群地平可完全取代结合，维拉帕米则部分取代结合，且在37℃时，10(-5)M地尔硫卓可使结合增强35%。对5例冠状动脉搭桥患者心脏直视手术获取的右心耳进行分析，结果相似（KD = 0.2±0.03 nM，Bmax = 42±2 fmol/mg蛋白质）。此外，对3只仓鼠心脏在死亡时或死后4℃或25℃下长达18小时进行检测，未发现KD或Bmax有显著差异。相比之下，与尸检或手术标本相比，梗阻性肥厚型心肌病患者的肌瘤切除标本中Bmax显著增加（110 fmol/mg蛋白质），而KD无变化（0.3 nM）。这些研究说明了直接在人心脏中研究钙通道的可行性和潜在优势。
