Extracellular calcium modulates generation of reactive oxygen species by the contracting diaphragm.
Extracellular calcium modulates generation of reactive oxygen species by the contracting diaphragm.
复制标题
细胞外钙通过收缩隔膜调节活性氧的产生。
DOI：
10.1152/jappl.1999.87.6.2177
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
DiMarco,A
中科院分区：
文献类型：
--
作者：
Supinski,G;Nethery,D;Stofan,D;DiMarco,A
最近的研究表明，在许多病理生理条件下，自由基可能在肌肉功能障碍的发展中起重要作用。因为在这些条件中的一些条件中观察到的肌肉功能障碍的程度似乎是自由基依赖性的并且受到细胞外钙浓度的调节，所以我们认为这两种现象之间可能存在联系;即，肌肉产生自由基的倾向可能取决于细胞外钙浓度。出于这个原因，我们比较了活性氧物质（ROS;即，自由基）的大鼠横膈膜（20-Hz刺激10分钟的序列，序列速率0.25序列/秒），在充满含有低（1 mM）、正常（2.5 mM）或高（5 mM）钙水平的生理溶液的器官浴中孵育。通过测量氢乙啶向乙锭的转化来评估ROS的产生。我们发现，随着细胞外钙水平的不同，收缩时ROS的产生也不同，在低钙研究中，ROS的产生较低（3.18 ± 0.40 ng/mg组织），而在正常钙（18.90 ± 2.70 ng/mg）或高钙（19.30 ± 4.50 ng/mg）研究中，ROS的产生要高得多（P< 0.001）。对照组，非收缩横膈膜（2.5 mM钙）几乎没有ROS产生（3.40 ± 0.80 ng/mg;P< 0.001）。为了进一步研究这个问题，我们将尼莫地平（20 μM），一种L型钙通道阻滞剂，加入收缩的横膈膜（2.5 mM钙浴），发现尼莫地平也抑制ROS形成（2.56 ± 0.85 ng乙锭/mg组织）。这些数据表明，活性氧产生的收缩隔膜强烈影响细胞外钙离子浓度，并可能依赖于通过L-型钙通道的钙转运。
Recent studies have indicated that free radicals may play an important role in the development of muscle dysfunction in many pathophysiological conditions. Because the degree of muscle dysfunction observed in some of these conditions appears to be both free radical dependent and modulated by extracellular calcium concentrations, we thought that there may be a link between these two phenomena; i.e., the propensity of a muscle to generate free radicals may be dependent on extracellular calcium concentrations. For this reason, we compared formation of reactive oxygen species (ROS; i.e., free radicals) by electrically stimulated rat diaphragms (trains of 20-Hz stimuli for 10 min, train rate 0.25 trains/s) incubated in organ baths filled with physiological solutions containing low (1 mM), normal (2.5 mM), or high (5 mM) calcium levels. Generation of ROS was assessed by measuring the conversion of hydroethidine to ethidium. We found ROS generation with contraction varied with the extracellular calcium level, with low ROS production (3.18 ± 0.40 ng ethidium/mg tissue) for low-calcium studies and with much higher ROS generation for normal-calcium (18.90 ± 2.70 ng/mg) or high-calcium (19.30 ± 4.50 ng/mg) studies (P< 0.001). Control, noncontracting diaphragms (in 2.5 mM calcium) had little ROS production (3.40 ± 0.80 ng/mg;P< 0.001). To further investigate this issue, we added nimodipine (20 μM), an L-type calcium channel blocker, to contracting diaphragms (2.5 mM calcium bath) and found that nimodipine also suppressed ROS formation (2.56 ± 0.85 ng ethidium/mg tissue). These data indicate that ROS generation by the contracting diaphragm is strongly influenced by extracellular calcium concentrations and may be dependent on calcium transport through L-type calcium channels.