Role of mitochondria in the generation of spontaneous activity in detrusor smooth muscles of the Guinea pig bladder.
Role of mitochondria in the generation of spontaneous activity in detrusor smooth muscles of the Guinea pig bladder.
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DOI：
10.1097/01.ju.0000069428.46133.d5
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发表时间：
2003-08
期刊：
影响因子：
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通讯作者：
Y. Kubota;H. Hashitani;H. Fukuta;Hiroki Kubota;K. Kohri;Hikaru Suzuki
中科院分区：
文献类型：
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作者：
Y. Kubota;H. Hashitani;H. Fukuta;Hiroki Kubota;K. Kohri;Hikaru Suzuki
胃肠平滑肌节律性电活动与线粒体Ca ~（2+）处理有关。我们研究了线粒体在逼尿肌平滑肌自发活动中的作用。材料与方法分别采用常规微电极技术和Fura-PE 3（Calbiochem，San Diego，加州）荧光法测定豚鼠逼尿肌平滑肌膜电位和细胞内Ca 2+浓度（[Ca 2 +]i）的变化。结果逼尿肌平滑肌细胞出现自发性动作电位，并伴有[Ca 2 +]i的瞬时升高（Ca瞬变）。线粒体质子载体CCCP（羰基氰间氯苯腙）（10 μ M）去极化膜，增加[Ca 2 +]i，并引起激活，随后抑制动作电位和钙瞬变。高钾溶液钾浓度（[K+]o = 30 mM）去极化膜，并增加[Ca 2 +]i的水平类似于10 μ M CCCP产生的水平，但这种去极化不抑制动作电位。硝苯地平（10 μ M）降低CCCP诱导的[Ca 2 +]i增加幅度约50%。CCCP诱导的[Ca 2 +]i增加在无Ca 2+溶液中进一步降低约70%，在10 μ M SKF 96365（一种钙池操作性钙内流阻断剂）存在下降低约30%。在存在10 μ M硝苯地平和10 μ M环匹阿尼酸的情况下，CCCP诱导的[Ca 2 +]i反应被抑制至对照值的约25%。在这些条件下，重复应用10 μ M氯化乙酰胆碱连续降低[Ca 2 +]i反应，最终未能增加[Ca 2 +]i。随后的CCCP未能升高[Ca 2 +]i。结论线粒体在膀胱平滑肌钙缓冲中起重要作用。线粒体Ca 2+的供应可能是由Ca 2+从内部存储的运输，也通过非选择性阳离子通道的容性钙进入。线粒体Ca 2+处理也可能是逼尿肌平滑肌自发活动产生的关键。
PURPOSE The rhythmic electrical activity of gastrointestinal smooth muscles is associated with mitochondrial Ca2+ handling. We examined the role of mitochondria in the generation of spontaneous activity in detrusor smooth muscles. MATERIALS AND METHODS Changes in the membrane potential and intracellular Ca2+ concentration ([Ca2+]i) were measured in detrusor smooth muscles of the guinea pig using conventional microelectrode techniques and Fura-PE3 (Calbiochem, San Diego, California) fluorescence, respectively. RESULTS Detrusor smooth muscle cells showed spontaneous action potentials and associated transient increases in [Ca2+]i (Ca transients). The mitochondrial protonophore CCCP (carbonyl cyanide m-chlorophenyl hydrazone) (10 microM) depolarized the membrane, increased [Ca2+]i and caused activation followed by suppression of action potentials and Ca transients. High K solution potassium concentration ([K+]o = 30 mM) depolarized the membrane and increased [Ca2+]i to levels similar to those produced by 10 microM CCCP but this depolarization did not suppress action potentials. Nifedipine (10 microM) decreased the amplitude of CCCP induced increases in [Ca2+]i by about 50%. CCCP induced increases in [Ca2+]i were further reduced by about 70% in Ca2+-free solution and by about 30% in the presence of 10 microM SKF96365, a blocker for store operated Ca entry. In the presence of 10 microM nifedipine and 10 microM cyclopiazonic acid, CCCP induced [Ca2+]i responses were suppressed to about 25% of control values. Under these conditions repetitive applications of 10 microM acetylcholine chloride successively decreased [Ca2+]i responses and finally failed to increase [Ca2+]i. Subsequent CCCP failed to elevate [Ca2+]i. CONCLUSIONS These results suggest that mitochondria have an important role in Ca2+ buffering in bladder smooth muscles. Mitochondrial Ca2+ is presumably supplied by Ca2+ transport from internal stores and also by capacitative calcium entry through nonselective cation channels. Mitochondrial Ca2+ handling may also be critical for the generation of spontaneous activity in detrusor smooth muscle.