Bers D M, Bridge J H, MacLeod K T
Can J Physiol Pharmacol. 1987 Apr;65(4):610-8. doi: 10.1139/y87-103.
Cellular Ca uptake and efflux in rabbit ventricular muscle was measured using double-barreled Ca microelectrodes in the extracellular space. When repetitive stimulation was stopped there was a slow loss of cellular Ca. Upon resumption of stimulation Ca was taken up by the cells. These Ca movements are thought to represent the loss of Ca from the sarcoplasmic reticulum and the cell during rest and the refilling of the sarcoplasmic reticulum during stimulation. Ryanodine (100 nM) greatly enhanced both the efflux of Ca during rest and the uptake of Ca induced by stimulation. These results are consistent with the conclusions drawn below, but they are dependent upon the interpretation that these extracellular Ca depletions are indicative of sarcoplasmic reticulum Ca movements. To examine further this process, contractures induced by rapid cooling to 0 degrees C were used as an independent assay of sarcoplasmic reticulum Ca content. These rapid cooling contractures were smaller after longer rest intervals (declining with a half time of 1.5 min). In the presence of ryanodine, the rapid cooling contracture immediately after a contraction was greater than that seen under control conditions. However, in the presence of ryanodine these rapid cooling contractures decline as a function of rest duration with a half time of about 1 s. These results suggest that in the presence of ryanodine the sarcoplasmic reticulum can still take up Ca, but that it also loses this Ca very rapidly at the onset of rest.(ABSTRACT TRUNCATED AT 250 WORDS)
利用细胞外空间中的双管钙微电极测量了兔心室肌细胞的钙摄取和外流。当重复刺激停止时，细胞内的钙会缓慢流失。重新开始刺激时，细胞会摄取钙。这些钙的移动被认为代表了静息时肌浆网和细胞内钙的流失以及刺激时肌浆网的再充盈。Ryanodine（100 nM）极大地增强了静息时钙的外流以及刺激诱导的钙摄取。这些结果与以下得出的结论一致，但它们依赖于这样一种解释，即这些细胞外钙的消耗表明了肌浆网钙的移动。为了进一步研究这个过程，将快速冷却至0摄氏度诱导的挛缩用作肌浆网钙含量的独立检测方法。较长的静息间隔后，这些快速冷却挛缩变小（以1.5分钟的半衰期下降）。在存在Ryanodine的情况下，收缩后立即出现的快速冷却挛缩大于对照条件下所见。然而，在存在Ryanodine的情况下，这些快速冷却挛缩随着静息持续时间以约1秒的半衰期下降。这些结果表明，在存在Ryanodine的情况下，肌浆网仍能摄取钙，但在静息开始时也会非常迅速地失去这些钙。（摘要截取自250字）
