Department of Physiology and Biophysics, University of Washington, Seattle, 98195, USA.
Am J Physiol Heart Circ Physiol. 2011 Dec;301(6):H2285-94. doi: 10.1152/ajpheart.00488.2011. Epub 2011 Oct 7.
Ca(+) sparklets are subcellular Ca(2+) signals produced by the opening of sarcolemmal L-type Ca(2+) channels. Ca(2+) sparklet activity varies within the sarcolemma of arterial myocytes. In this study, we examined the relationship between Ca(2+) sparklet activity and sarcoplasmic reticulum (SR) Ca(2+) accumulation and release in cerebral arterial myocytes. Our data indicate that the SR is a vast organelle with multiple regions near the sarcolemma of these cells. Ca(2+) sparklet sites were located at or <0.2 μm from SR-sarcolemmal junctions. We found that while Ca(2+) sparklets increase the rate of SR Ca(2+) refilling in arterial myocytes, their activity did not induce regional variations in SR Ca(2+) content or Ca(2+) spark activity. In arterial myocytes, L-type Ca(2+) channel activity was independent of SR Ca(2+) load. This ruled out a potential feedback mechanism whereby SR Ca(2+) load regulates the activity of these channels. Together, our data suggest a model in which Ca(2+) sparklets contribute Ca(2+) influx into a cytosolic Ca(2+) pool from which sarco(endo)plasmic reticulum Ca(2+)-ATPase pumps Ca(2+) into the SR, indirectly regulating SR function.
钙火花是由肌质网膜 L 型钙通道开放产生的亚细胞钙信号。钙火花活动在动脉肌细胞的肌质网中变化。在这项研究中，我们研究了钙火花活动与脑动脉肌细胞肌质网（SR）钙积累和释放之间的关系。我们的数据表明，SR 是一个巨大的细胞器，在这些细胞的肌质网附近有多个区域。钙火花位点位于或距 SR-肌质网连接处 0.2μm 以内。我们发现，虽然钙火花增加了动脉肌细胞中 SR 钙再填充的速率，但它们的活动并没有引起 SR 钙含量或钙火花活动的区域变化。在动脉肌细胞中，L 型钙通道的活性与 SR 钙负荷无关。这排除了一种潜在的反馈机制，即 SR 钙负荷调节这些通道的活性。总之，我们的数据表明了一种模型，即钙火花将钙内流到细胞质钙池中，肌浆网（内）钙 ATP 酶将钙泵入 SR，间接调节 SR 的功能。
