Fabiato A, Fabiato F
Nature. 1979 Sep 13;281(5727):146-8. doi: 10.1038/281146a0.
It has been proposed that the trans-sarcolemmal influx of Ca2+ occurring during the plateau of the mammalian cardiac action potentials is insufficient in itself to activate the myofilaments, but can trigger a release of Ca2+ from the sarcoplasmic reticulum (SR) which is sufficient for activation. The demonstration of this Ca2+-induced release of Ca2+ relied entirely on experiments in which the tension developed by the myofilaments was used as a sensor of the changes of myoplasmic free Ca2+ concentration ([free Ca2+]) in segments of single cardiac cells from which the sarcolemma had been removed by microdissection (skinned cardiac cells). The small size of these preparations has previously prevented the use of more direct methods for the detection of myoplasmic Ca2+ movements. The present study is a direct demonstration of Ca2+-induced release of Ca2+ from the SR of skinned cardiac cells treated with chlorotetracycline (CTC), a fluorescent chelate probe which enables changes in the amount of Ca2+ bound to a variety of biological membranes or micelles to be monitored. The fluorescence increases when more Ca2+ is bound.
有人提出，在哺乳动物心脏动作电位平台期发生的Ca2+跨肌膜内流本身不足以激活肌丝，但可触发肌浆网（SR）释放Ca2+，而这一释放量足以激活肌丝。这种Ca2+诱导的Ca2+释放的证明完全依赖于这样的实验，即肌丝产生的张力被用作微解剖去除肌膜的单个心脏细胞片段中肌浆游离Ca2+浓度（[游离Ca2+]）变化的传感器（脱膜心脏细胞）。这些标本体积小，以前阻碍了使用更直接的方法来检测肌浆Ca2+运动。本研究直接证明了用氯四环素（CTC）处理的脱膜心脏细胞的SR中Ca2+诱导的Ca2+释放，CTC是一种荧光螯合探针，能够监测与各种生物膜或微团结合的Ca2+量的变化。当结合更多Ca2+时，荧光增强。
