Kuo Kuo-Hsing, Dai Jiazhen, Seow Chun Yong, Lee Cheng-Han, van Breemen Cornelis
St. Paul's Hospital, The iCAPTURE Center, University of British Columbia, Vancouver, British Columbia V6Z 1Y6, Canada.
Am J Physiol Lung Cell Mol Physiol. 2003 Dec;285(6):L1345-53. doi: 10.1152/ajplung.00043.2003. Epub 2003 Aug 22.
Fluctuations in intracellular calcium concentration ([Ca2+]i) constitute the main link in excitation-contraction coupling (E-C coupling) in airway smooth muscle cells (ASMC). It has recently been reported that ACh induces asynchronous recurring Ca2+ waves in intact ASMC of murine bronchioles. With the use of a novel technique allowing us to simultaneously measure subcellular [Ca2+]i and force generation in ASMC located within an intact tracheal muscle bundle, we examined a similar pattern of Ca2+ signaling in the trachea. We found that application of ACh resulted in the generation of recurring intracellular Ca2+ waves progressing along the longitudinal axis of the ribbon-shaped intact ASMC. These Ca2+ waves were not synchronized between neighboring cells, and induction of wave-like [Ca2+]i oscillations was temporally associated with development of force by the tracheal muscle bundle. By comparing the concentration dependence of force generation and the parameters characterizing the [Ca2+]i oscillations, we found that the concentration-dependent increase in ACh-induced force development by the tracheal smooth muscle bundle is achieved by differential recruitment of intact ASMC to initiate Ca2+ waves and by enhancement in the frequency of [Ca2+]i oscillations and elevation of interspike [Ca2+]i once the cells are recruited. Our findings demonstrate that asynchronous recurring Ca2+ waves underlie E-C coupling in ACh-induced contraction of the intact tracheal smooth muscle bundle. Furthermore, in contrast to what was reported in enzymatically dissociated ASMC, Ca2+ influx through the L-type voltage-gated Ca2+ channel was not an obligatory requirement for the generation of [Ca2+]i oscillations and development of force in ACh-stimulated intact ASMC.
细胞内钙浓度（[Ca2+]i）的波动是气道平滑肌细胞（ASMC）兴奋-收缩偶联（E-C偶联）的主要环节。最近有报道称，乙酰胆碱（ACh）可在小鼠细支气管完整的ASMC中诱导异步反复出现的Ca2+波。利用一种新技术，我们能够同时测量完整气管肌束内ASMC的亚细胞[Ca2+]i和力的产生，据此我们研究了气管中类似的Ca2+信号模式。我们发现，施加ACh会导致反复出现的细胞内Ca2+波产生，这些波沿带状完整ASMC的纵轴传播。相邻细胞之间的这些Ca2+波并不同步，并且[Ca2+]i振荡样的诱导在时间上与气管肌束的力发展相关。通过比较力产生的浓度依赖性和表征[Ca2+]i振荡的参数，我们发现气管平滑肌束对ACh诱导的力发展的浓度依赖性增加是通过差异募集完整的ASMC以启动Ca2+波，以及在细胞被募集后提高[Ca2+]i振荡频率和峰间[Ca2+]i来实现的。我们的研究结果表明，异步反复出现的Ca2+波是完整气管平滑肌束ACh诱导收缩中E-C偶联的基础。此外，与酶解ASMC中的报道不同，在ACh刺激的完整ASMC中，通过L型电压门控Ca2+通道的Ca2+内流不是产生[Ca2+]i振荡和力发展的必要条件。
