Davia K, Davies C H, Harding S E
National Heart and Lung Institute, Imperial College, London, UK.
Cardiovasc Res. 1997 Jan;33(1):88-97. doi: 10.1016/s0008-6363(96)00187-3.
There has been debate regarding the level of sarcoplasmic reticulum (SR) Ca2+ ATPase protein in heart failure. We have used the SR Ca2+ ATPase inhibitor thapsigargin to investigate the functional contribution of this uptake system to contraction and relaxation in myocytes from failing and non-failing human ventricle.
Myocytes were isolated from 28 failing and 18 non-failing ventricles and stimulated at 0.2 Hz, 32 degrees C in Krebs-Henseleit solution. Contraction amplitude and speed were compared before and after treatment with 1 mumol/l thapsigargin for 20 min to deplete SR Ca2+ stores.
Initial beat duration was longer in myocytes from failing hearts. Addition of thapsigargin significantly prolonged the beat in myocytes from both groups, but the increase was greater in non-failing hearts (beat duration increased by 0.79 +/- 0.12 s in myocytes from non-failing hearts compared with 0.37 +/- 0.12 s in those from failing, P < 0.02). The contraction amplitude increased at high stimulation frequencies in myocytes from non-failing hearts (from 2.6% shortening at 0.1 Hz to 4.6% at 1 Hz, P < 0.001, n = 9), but not in those from failing hearts (1.8% at 0.1 Hz compared with 1.7% at 1 Hz, n = 5). Thapsigargin abolished the positive staircase in the non-failing, but had no effect in the failing group. Contraction amplitude following a rest interval was significantly depressed relative to steady-state levels in myocytes from the non-failing hearts (44.8 +/- 10.3% at 3 min), but not in failing (102 +/- 18%, P < 0.01 compared to non-failing at 3 min). Following thapsigargin treatment, there were no longer significant differences between failing and non-failing myocytes in the time course of the beat, frequency response or post-rest behaviour.
The differences between myocytes from failing and non-failing hearts were reduced by inhibition of SR function. These results are consistent with the hypothesis that the initial differences had been due to decreased SR Ca2+ uptake.
关于心力衰竭时肌浆网（SR）Ca2+ATP酶蛋白水平一直存在争议。我们使用SR Ca2+ATP酶抑制剂毒胡萝卜素，来研究这种摄取系统对衰竭和非衰竭人心室肌细胞收缩和舒张的功能贡献。
从28个衰竭心室和18个非衰竭心室中分离出肌细胞，并在32℃的Krebs-Henseleit溶液中以0.2Hz的频率进行刺激。在用1μmol/L毒胡萝卜素处理20分钟以耗尽SR Ca2+储备之前和之后，比较收缩幅度和速度。
衰竭心脏的肌细胞初始搏动持续时间更长。添加毒胡萝卜素显著延长了两组肌细胞的搏动时间，但非衰竭心脏的增加幅度更大（非衰竭心脏的肌细胞搏动持续时间增加了0.79±0.12秒，而衰竭心脏的肌细胞为0.37±0.12秒，P<0.02）。非衰竭心脏的肌细胞在高刺激频率下收缩幅度增加（从0.1Hz时的缩短2.6%增加到1Hz时的4.6%，P<0.001，n=9），而衰竭心脏的肌细胞则没有（0.1Hz时为1.8%，1Hz时为1.7%，n=5）。毒胡萝卜素消除了非衰竭组中的正阶梯现象，但对衰竭组没有影响。相对于非衰竭心脏的肌细胞的稳态水平，休息间隔后的收缩幅度显著降低（3分钟时为44.8±10.3%），但衰竭心脏的肌细胞没有（102±18%，与3分钟时的非衰竭心脏相比P<0.01）。在用毒胡萝卜素处理后，衰竭和非衰竭肌细胞在搏动时间过程、频率反应或休息后行为方面不再有显著差异。
通过抑制SR功能，衰竭和非衰竭心脏的肌细胞之间的差异减小。这些结果与最初的差异是由于SR Ca2+摄取减少的假设一致。
