Lee Sunwoo, Kim Joon-Chul, Li Yuhua, Son Min-Jeong, Woo Sun-Hee
College of Pharmacy, Chungnam National University, Yuseong-Gu, Daejeon 305-764, South Korea.
Am J Physiol Cell Physiol. 2008 Apr;294(4):C966-76. doi: 10.1152/ajpcell.00381.2007. Epub 2008 Feb 13.
This study examines whether fluid pressure (FP) modulates the L-type Ca(2+) channel in cardiomyocytes and investigates the underlying cellular mechanism(s) involved. A flow of pressurized (approximately 16 dyn/cm(2)) fluid, identical to that bathing the myocytes, was applied onto single rat ventricular myocytes using a microperfusion method. The Ca(2+) current (I(Ca)) and cytosolic Ca(2+) signals were measured using a whole cell patch-clamp and confocal imaging, respectively. It was found that the FP reversibly suppressed I(Ca) (by 25%) without altering the current-voltage relationships, and it accelerated the inactivation of I(Ca). The level of I(Ca) suppression by FP depended on the level and duration of pressure. The Ba(2+) current through the Ca(2+) channel was only slightly decreased by the FP (5%), suggesting an indirect inhibition of the Ca(2+) channel during FP stimulation. The cytosolic Ca(2+) transients and the basal Ca(2+) in field-stimulated ventricular myocytes were significantly increased by the FP. The effects of the FP on the I(Ca) and on the Ca(2+) transient were resistant to the stretch-activated channel inhibitors, GsMTx-4 and streptomycin. Dialysis of myocytes with high concentrations of BAPTA, the Ca(2+) buffer, eliminated the FP-induced acceleration of I(Ca) inactivation and reduced the inhibitory effect of the FP on I(Ca) by approximately 80%. Ryanodine and thapsigargin, abolishing sarcoplasmic reticulum Ca(2+) release, eliminated the accelerating effect of FP on the I(Ca) inactivation, and they reduced the inhibitory effect of FP on the I(Ca). These results suggest that the fluid pressure indirectly suppresses the Ca(2+) channel by enhancing the Ca(2+)-induced intracellular Ca(2+) release in rat ventricular myocytes.
本研究检测流体压力（FP）是否调节心肌细胞中的L型Ca(2+)通道，并探究其中潜在的细胞机制。使用微量灌注法将与心肌细胞浴液相同的加压（约16达因/平方厘米）流体流施加到单个大鼠心室肌细胞上。分别使用全细胞膜片钳和共聚焦成像测量Ca(2+)电流（I(Ca)）和胞质Ca(2+)信号。结果发现，FP可使I(Ca)可逆性抑制（降低25%），而不改变电流-电压关系，并且加速I(Ca)的失活。FP对I(Ca)的抑制程度取决于压力水平和持续时间。通过Ca(2+)通道的Ba(2+)电流仅被FP轻微降低（5%），提示在FP刺激期间对Ca(2+)通道存在间接抑制作用。FP可使电场刺激的心室肌细胞中的胞质Ca(2+)瞬变和基础Ca(2+)显著增加。FP对I(Ca)和Ca(2+)瞬变的作用不受牵张激活通道抑制剂GsMTx-4和链霉素的影响。用高浓度Ca(2+)缓冲剂BAPTA对心肌细胞进行透析，消除了FP诱导的I(Ca)失活加速，并使FP对I(Ca)的抑制作用降低约80%。ryanodine和毒胡萝卜素可消除肌浆网Ca(2+)释放，它们消除了FP对I(Ca)失活的加速作用，并降低了FP对I(Ca)的抑制作用。这些结果提示，流体压力通过增强大鼠心室肌细胞中Ca(2+)诱导的细胞内Ca(2+)释放来间接抑制Ca(2+)通道。
