Steenbergen C, Murphy E, Levy L, London R E
Circ Res. 1987 May;60(5):700-7. doi: 10.1161/01.res.60.5.700.
Changes in cytosolic free calcium concentration during myocardial ischemia were measured by 19F NMR in 5FBAPTA-loaded perfused rat hearts. The hearts were perfused with Krebs-Henseleit buffer containing 5 microM of the acetoxymethyl ester of 5FBAPTA, which was hydrolyzed by cytosolic esterases to achieve cytosolic concentrations of 5FBAPTA of 0.12 to 0.65 mM. Cytosolic free calcium concentrations were calculated as the product of the ratio of peak areas for bound and free 5FBAPTA in the NMR spectra and the dissociation constant (708 nM). The basal cytosolic calcium concentration, measured in potassium or magnesium arrested hearts, was 252 nM, and the time-average calcium concentration in beating hearts was 630 nM. Following the onset of total ischemia, there was no immediate substantial change in cytosolic calcium despite a rapid decline in creatine phosphate and ATP and a marked increase in inorganic phosphate as monitored by 31P NMR, but by 10 minutes, there was a substantial increase in free calcium concentration. The ratio of peak areas of bound and free 5FBAPTA returned to the preischemic value during reperfusion, and there was no detectable loss of 5FBAPTA from the heart. Creatine phosphate was also restored to its preischemic level during reperfusion. These results indicate that cytosolic free calcium increases during ischemia and is not immediately associated with lethal injury. This increase in cytosolic calcium may activate degradative enzymes that eventually could compromise myocyte viability.
在5FBAPTA负载的灌注大鼠心脏中，通过19F核磁共振测量心肌缺血期间胞质游离钙浓度的变化。心脏用含有5微摩尔5FBAPTA乙酰氧基甲酯的Krebs-Henseleit缓冲液灌注，该酯被胞质酯酶水解，以达到胞质中5FBAPTA浓度为0.12至0.65毫摩尔。胞质游离钙浓度通过核磁共振谱中结合态和游离态5FBAPTA峰面积之比与解离常数（708纳摩尔）的乘积来计算。在钾或镁停搏的心脏中测得的基础胞质钙浓度为252纳摩尔，跳动心脏中的时间平均钙浓度为630纳摩尔。完全缺血开始后，尽管通过31P核磁共振监测发现磷酸肌酸和三磷酸腺苷迅速下降，无机磷酸盐显著增加，但胞质钙没有立即出现实质性变化，但到10分钟时，游离钙浓度大幅增加。再灌注期间，结合态和游离态5FBAPTA的峰面积比恢复到缺血前的值，并且没有检测到心脏中5FBAPTA的损失。再灌注期间磷酸肌酸也恢复到缺血前水平。这些结果表明，胞质游离钙在缺血期间增加，并且与致命损伤没有直接关联。胞质钙的这种增加可能会激活降解酶，最终可能损害心肌细胞活力。
