Clemens M G, Forrester T
Q J Exp Physiol. 1982 Oct;67(4):655-62. doi: 10.1113/expphysiol.1982.sp002684.
The deleterious effect of calcium withdrawal and restoration on cardiac cell membranes ('Ca-paradox') was studied using isolated, working rat heart. The optical density of the coronary sinus effluent was measured at 260 nm wavelength. The efflux of A260 material upon restoration of calcium was proportional to the duration of calcium-free perfusion, indicating graded membraneous injury. When ATP, 10(-6) to 10(-4) M, was added to the calcium-free perfusate for 30 s of calcium-free perfusion, release of A260 material increased as a logarithmic function of exogenous ATP concentration. That this exacerbating effect is produced by such low concentrations relative to intracellular amounts indicates an action of ATP on the membrane surface. It is suggested that exogenous ATP enhances calcium entry into the cell, thus contributing to calcium influx through membranes already rendered abnormally permeable from the 'Ca-paradox' mechanism.
利用离体工作大鼠心脏研究了钙撤离和恢复对心肌细胞膜的有害作用（“钙反常”）。在260nm波长下测量冠状窦流出液的光密度。钙恢复时A260物质的流出与无钙灌注持续时间成正比，表明存在分级的膜损伤。当在无钙灌注液中加入10(-6)至10(-4)M的ATP并进行30秒的无钙灌注时，A260物质的释放量随外源ATP浓度呈对数函数增加。相对于细胞内含量而言，如此低的浓度就能产生这种加剧作用，这表明ATP作用于膜表面。提示外源ATP增强钙进入细胞，从而促使钙通过因“钙反常”机制已变得异常通透的膜流入。
