Quinn T, Molloy M, Smyth A, Baird A W
Department of Veterinary Physiology and Biochemistry, Faculty of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
Life Sci. 2004 Feb 13;74(13):1659-69. doi: 10.1016/j.lfs.2003.08.030.
This study investigates the involvement of capacitative Ca2+ entry in excitation-contraction coupling in guinea pig gallbladder smooth muscle. Thapsigargin (0.1 nM-1 microM, a sarcoplasmic reticulum Ca(2+)-ATPase inhibitor) produced slowly developing sustained tonic contractions in guinea pig isolated gallbladder strips. All contractions approached 50% of the response to carbachol (10 microM) after 55 min. Contractile responses to thapsigargin (1 microM) were abolished in a Ca(2+)-free medium. Subsequent re-addition of Ca2+ (2.5 mM) produced a sustained tonic contraction (99 +/- 6% of the carbachol response). The contractile response to Ca2+ re-addition following incubation of tissues in a Ca(2+)-free bathing solution in the absence of thapsigargin was significantly less than in its presence (79 +/- 4 % vs 100 +/- 7 % of carbachol; p < 0.05). Contractile responses to Ca2+ re-addition following treatment with thapsigargin were attenuated by (a) the L-type voltage-operated Ca2+ channel antagonist, nifedipine (10 microM) and (b) the general inhibitor of Ca2+ entry channels including store-operated channels, SK&F96365 (50 microM and 100 microM). In separate experiments, responses to Ca2+ re-addition were essentially abolished by the tyrosine kinase inhibitor, genistein (100 microM). These results suggest that capacitative Ca2+ entry provides a source of activator Ca2+ for guinea pig gallbladder smooth muscle contraction. Contractile responses to Ca2+ re-addition following depletion of sarcoplasmic reticulum Ca2+ stores with thapsigargin, are mediated in part by Ca2+ entry through voltage-operated Ca2+ channels and by capacitative Ca2+ entry through store-operated Ca2+ channels which can be blocked by SK&F96365. Furthermore, capacitative Ca2+ entry in this tissue may be modulated by tyrosine kinase.
本研究调查了容量性Ca2+内流在豚鼠胆囊平滑肌兴奋-收缩偶联中的作用。毒胡萝卜素（0.1 nM - 1 μM，一种肌浆网Ca(2+)-ATP酶抑制剂）在豚鼠离体胆囊条上产生缓慢发展的持续性强直收缩。55分钟后，所有收缩接近对卡巴胆碱（10 μM）反应的50%。在无Ca(2+)的培养基中，对毒胡萝卜素（1 μM）的收缩反应消失。随后重新添加Ca2+（2.5 mM）产生持续性强直收缩（为卡巴胆碱反应的99 ± 6%）。在无毒胡萝卜素的情况下，将组织置于无Ca(2+)的浴液中孵育后再添加Ca2+，其收缩反应明显小于存在毒胡萝卜素时（分别为卡巴胆碱反应的79 ± 4%和100 ± 7%；p < 0.05）。用毒胡萝卜素处理后再添加Ca2+的收缩反应，被（a）L型电压门控Ca(2+)通道拮抗剂硝苯地平（10 μM）和（b）包括储存-操纵通道在内的Ca(2+)内流通道的通用抑制剂SK&F96365（50 μM和100 μM）减弱。在单独的实验中，酪氨酸激酶抑制剂染料木黄酮（100 μM）基本消除了对再添加Ca2+的反应。这些结果表明，容量性Ca2+内流为豚鼠胆囊平滑肌收缩提供了激活Ca2+的来源。用毒胡萝卜素耗尽肌浆网Ca2+储存后再添加Ca2+的收缩反应，部分是由通过电压门控Ca(2+)通道的Ca(2+)内流和通过可被SK&F96365阻断的储存-操纵Ca(2+)通道的容量性Ca2+内流介导的。此外，该组织中的容量性Ca2+内流可能受酪氨酸激酶调节。
