Relations between excitability and contractility in rat soleus muscle:: role of the Na+-K+ pump and Na+/K+ gradients
Relations between excitability and contractility in rat soleus muscle:: role of the Na+-K+ pump and Na+/K+ gradients
复制标题
DOI：
10.1111/j.1469-7793.1999.0215r.x
复制
发表时间：
1999-07-01
影响因子：
5.5
通讯作者：
Clausen, T
中科院分区：
文献类型：
--
作者：
Overgaard, K;Nielsen, OB;Clausen, T
1. 研究了Na+/K+梯度降低和Na+-K+泵刺激对大鼠离体比目鱼肌复合动作电位（M波）和收缩力的影响。与含有147 mM Na+和4 mM K+的标准缓冲液的对照水平相比，将肌肉暴露于含有85 mM Na+和9 mM K+的缓冲液（85 Na+/9 K+缓冲液）中，M波面积减少54%，强直力减少50%。随后使用β(2)-肾上腺素能受体激动剂沙丁胺醇刺激或激活Na+-K+转运，诱导M波面积和破伤风力显著恢复（分别达到对照水平的98%和87%）。同样，用胰岛素刺激Na+-K+的活性运输也能显著恢复M波面积和强直性。在85 Na+/9 K+缓冲液平衡和添加沙丁胺醇后，M波面积与破伤风力呈密切线性相关（r = 0.92, P < 0.001）。在使用河豚毒素降低兴奋性的肌肉和在频率为30赫兹的连续刺激120秒后疲劳的肌肉中发现了类似的相关性。这些结果表明，兴奋性与强直力密切相关。此外，在因Na+/K+梯度降低而抑制的肌肉中，Na+-K+泵的β -肾上腺素能刺激可诱导兴奋性恢复，这可以充分解释先前证明的Na+-K+泵刺激后破伤风力的恢复。此外，数据表明，兴奋性丧失是高频（30 Hz）刺激引起疲劳的重要因素。
1. The effects of reduced Na+/K+ gradients and Na+-K+ pump stimulation on compound action potentials (M waves) and contractile force were examined in isolated rat soleus muscles stimulated through the nerve.2. Exposure of muscles to buffer containing 85 mM Na+ and 9 mM K+ (85 Na+/9 K+ buffer) produced a 54 % decrease in M wave area and a 50 % decrease in tetanic force compared with control levels in standard buffer containing 147 mM Na+ and 4 mM K+. Subsequent stimulation or active Na+-K+ transport, using the beta(2)-adrenoceptor agonist salbutamol, induced a marked recovery of M wave area and tetanic force (to 98 and 87 % of the control level, respectively). Similarly, stimulation of active Na+-K+ transport with insulin induced a significant recovery of M wave area and tetanic force.3. During equilibration with 85 Na+/9 K+ buffer and after addition of salbutamol there was a close linear correlation between M wave area and tetanic force (r = 0.92, P < 0.001). Similar correlations were found in muscles where tetrodotoxin was used to reduce excitability and in muscles fatigued by 120 s of continuous stimulation at a frequency of 30 Hz.4. These results show a close correlation between excitability and tetanic force. Furthermore, in muscles depressed by a reduction in the Na+/K+ gradients, beta-adrenergic stimulation of the Na+-K+ pump induces a recovery of excitability which can fully explain the previously demonstrated recovery of tetanic force following Na+-K+ pump stimulation. Moreover, the data indicate that loss of excitability is an important factor in fatigue induced by high frequency (30 Hz) stimulation.