Kubota Yasue, Hashitani Hikaru, Fukuta Hiroyasu, Kubota Hiroki, Kohri Kenjiro, Suzuki Hikaru
Department of Physiology, Nagoya City University Medical School, Nagoya, Japan.
J Urol. 2003 Aug;170(2 Pt 1):628-33. doi: 10.1097/01.ju.0000069428.46133.d5.
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.
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.
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.
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.
胃肠道平滑肌的节律性电活动与线粒体钙处理有关。我们研究了线粒体在逼尿肌平滑肌自发活动产生中的作用。
分别使用传统微电极技术和Fura - PE3（Calbiochem，圣地亚哥，加利福尼亚）荧光法测量豚鼠逼尿肌平滑肌的膜电位和细胞内钙浓度（[Ca2+]i）变化。
逼尿肌平滑肌细胞表现出自发动作电位以及相关的[Ca2+]i瞬时升高（钙瞬变）。线粒体质子载体CCCP（羰基氰化物间氯苯腙）（10微摩尔）使膜去极化，增加[Ca2+]i，并导致动作电位和钙瞬变先激活后抑制。高钾溶液（钾浓度[K+]o = 30毫摩尔）使膜去极化，并使[Ca2+]i升高至与10微摩尔CCCP产生的水平相似，但这种去极化并未抑制动作电位。硝苯地平（10微摩尔）使CCCP诱导的[Ca2+]i升高幅度降低约50%。在无钙溶液中，CCCP诱导的[Ca2+]i升高进一步降低约70%，在存在10微摩尔SKF96365（一种储存操作钙内流阻滞剂）时降低约30%。在存在10微摩尔硝苯地平和10微摩尔环匹阿尼酸的情况下，CCCP诱导的[Ca2+]i反应被抑制至对照值的约25%。在这些条件下，重复应用10微摩尔氯化乙酰胆碱会相继降低[Ca2+]i反应，最终无法增加[Ca2+]i。随后的CCCP未能升高[Ca2+]i。
这些结果表明线粒体在膀胱平滑肌的钙缓冲中起重要作用。线粒体钙大概由来自内部储存的钙转运以及通过非选择性阳离子通道的容量性钙内流提供。线粒体钙处理对于逼尿肌平滑肌自发活动的产生也可能至关重要。
