Inotropic and calcium kinetic effects of calcium channel agonist and antagonist in isolated cardiac myocytes from cardiomyopathic hamsters.
Inotropic and calcium kinetic effects of calcium channel agonist and antagonist in isolated cardiac myocytes from cardiomyopathic hamsters.
复制标题
钙通道激动剂和拮抗剂对心肌病仓鼠离体心肌细胞的正性肌力和钙动力学作用。
DOI：
10.1161/01.res.67.3.599
复制
发表时间：
1990
影响因子：
20.1
通讯作者：
Smith,TW
中科院分区：
文献类型：
--
作者：
Sen,LY;O'Neill,M;Marsh,JD;Smith,TW
心肌病（CM）仓鼠的心脏细胞钙超载的机制尚不清楚。我们使用8-9月龄CM仓鼠（BIO 14.6）和年龄匹配的正常对照的分离心肌细胞，检测了慢钙通道的数量、通过慢钙通道的钙摄取、钙池大小以及对Bay K 8644、维拉帕米和硝苯地平的收缩反应。通过[3 H] PN 200 -110的特异性结合评估的二氢吡啶结合位点的数量在两组中相似（对照心脏：Bmax = 333 +/- 89 [平均值+/- SD] fmol/mg; CM心脏：Bmax = 357 +/- 75 fmol/mg; n = 5次实验，p = 0.6）。使用全细胞钳技术（在-50 mV保持电位和-10 mV测试电位下）测定通过L型钙通道的电流密度，CM肌细胞（17.8 +/- 1.5 [平均值+/- SD] pA/pF）和对照肌细胞（18.6 +/- 2.1 pA/pF）中的电流密度相同（n = 5次实验，p = 0.5）。CM和对照细胞的电流-电压关系（测试电位从-40 mV变化到+50 mV）也相同，表观阈值、峰值电流和反转电位也相同。然而，45 Ca流入的初始速率以及快速交换钙池的大小显着大于从CM获得的心肌细胞比从正常仓鼠。在这两种肌细胞制剂中，Bay K 8644在60秒时使45 Ca摄取率增加25%;维拉帕米在正常和CM仓鼠中分别使60秒时45 Ca摄取率降低16%和17%。硝苯地平也有类似的抑制作用。由光学视频系统评估的驱动在1.5 Hz的细胞中的细胞运动的幅度随着细胞外钙或Bay K 8644在正常或CM仓鼠的心肌细胞中的浓度的增加而逐渐增加。然而，两种效应物的浓度-效应曲线在CM细胞中与来自正常仓鼠的细胞相比向左移动。两种制剂对维拉帕米和硝苯地平表现出相似的收缩反应。这些研究结果表明，单一的酶促解离的心肌细胞CM仓鼠有受损的收缩特性类似于那些在完整的心脏，从而提供了一个有用的实验系统，在其中研究潜在的细胞机制，在这个模型的心力衰竭。我们的结果进一步表明，CM仓鼠心肌细胞中的钙超载可能不是如之前所建议的那样，通过二氢吡啶敏感性钙通道增加的钙内流，而是由于细胞内钙稳态异常。
The mechanism by which heart cells of cardiomyopathic (CM) hamsters become calcium overloaded is not known. We examined the number of slow calcium channels, calcium uptake via slow calcium channels, calcium pool sizes, and the contractile response to Bay K 8644, verapamil, and nifedipine using isolated cardiac myocytes from 8-9-month-old CM hamsters (BIO 14.6) and age-matched normal controls. The number of dihydropyridine binding sites as assessed by specific binding of [3H]PN200-110 was similar in the two groups (control hearts: Bmax = 333 +/- 89 [mean +/- SD] fmol/mg; CM hearts: Bmax = 357 +/- 75 fmol/mg; n = 5 experiments, p = 0.6). Current density through L-type calcium channels was determined using the whole-cell clamp technique (at -50 mV holding potential and -10 mV test potential) and was the same in CM myocytes (17.8 +/- 1.5 [mean +/- SD] pA/pF) and control myocytes (18.6 +/- 2.1 pA/pF) (n = 5 experiments, p = 0.5). The current-voltage relation (test potentials varied from -40 to +50 mV) was also the same in CM and control cells, as was apparent threshold, peak current, and reversal potential. However, the initial rate of 45Ca influx as well as the size of the rapidly exchangeable calcium pool was significantly greater in myocytes obtained from CM than from normal hamsters. In both myocyte preparations, Bay K 8644 increased the rate of 45Ca uptake by 25% at 60 seconds; verapamil decreased 45Ca uptake at 60 seconds by 16% and 17% in normal and CM hamsters, respectively. A similar inhibitory effect was observed with nifedipine. The amplitude of cell motion in cells driven at 1.5 Hz as assessed by an optical-video system increased progressively with increasing concentrations of extracellular calcium or Bay K 8644 in cardiac myocytes from normal or CM hamsters. However, the concentration-effect curves for the two effectors were shifted to the left in CM cells compared with cells from normal hamsters. Both preparations demonstrated similar contractile responses to verapamil and nifedipine. These findings demonstrate that single enzymatically dissociated cardiac myocytes from CM hamsters have impaired contractile properties analogous to those seen in the intact heart and thus provide a useful experimental system in which to study underlying cellular mechanisms operative in this model of heart failure. Our results further indicate that calcium overload in CM hamster cardiac myocytes may not be due to increased calcium influx via dihydropyridine-sensitive calcium channels, as suggested previously, but rather to abnormalities of intracellular calcium homeostasis.