Wassdal I, Larsen K, Iversen J G
Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Norway.
Acta Physiol Scand. 1999 Mar;165(3):259-64. doi: 10.1046/j.1365-201x.1999.00509.x.
The effect of bradykinin on the cytosolic Ca2+ concentration were measured in single, Fura-2 loaded, smooth muscle cells isolated from rat duodenum. All cells responded with a Ca2+ signal when exposed to bradykinin. The bradykinin response consisted of an initial Ca2+ spike followed by a plateau. Pre-treatment of single muscle cells with either the phospholipase C blocker U-73122 or thapsigargin, which is a potent inhibitor of the endoplasmic reticulum Ca2+-ATPase, inhibited the response to bradykinin. Pre-treatment of the cells with EGTA or La3+ to inhibit the Ca2+ influx, abolished the response induced by bradykinin. We conclude that bradykinin applied to single smooth muscle cells from rat duodenum, increases cytosolic Ca2+ by emptying intracellular Ca2+ stores, and by contribution from extracellular Ca2+. In contrast to bradykinin-induced response in isolated rat duodenum (a relaxation followed by a contraction), we did not observe a biphasic effect of bradykinin on cytosolic Ca2+ in single muscle cells. Bradykinin may thus cause relaxation of duodenal smooth muscle indirectly through an effect on neighbouring cells as dilatation is brought about by this agent in blood vessels.
在从大鼠十二指肠分离出的单个、负载Fura-2的平滑肌细胞中，测量了缓激肽对胞质Ca2+浓度的影响。所有细胞在暴露于缓激肽时都会产生Ca2+信号。缓激肽反应包括一个初始的Ca2+峰值，随后是一个平台期。用磷脂酶C阻断剂U-73122或毒胡萝卜素（一种内质网Ca2+-ATP酶的有效抑制剂）对单个肌肉细胞进行预处理，可抑制对缓激肽的反应。用EGTA或La3+预处理细胞以抑制Ca2+内流，可消除缓激肽诱导的反应。我们得出结论，应用于大鼠十二指肠单个平滑肌细胞的缓激肽，通过排空细胞内Ca2+储存以及细胞外Ca2+的作用来增加胞质Ca2+。与缓激肽在离体大鼠十二指肠中诱导的反应（先舒张后收缩）相反，我们在单个肌肉细胞中未观察到缓激肽对胞质Ca2+的双相作用。因此，缓激肽可能通过对邻近细胞的作用间接导致十二指肠平滑肌舒张，因为该物质在血管中可引起扩张。
