Brinley F J, Tiffert T, Scarpa A
J Gen Physiol. 1978 Jul;72(1):101-27. doi: 10.1085/jgp.72.1.101.
Continuous nondestructive monitoring of intracellular ionized calcium in isolated squid axons by differential absorption spectroscopy (using arsenazo III and antipyrylazo III) was used to study uptake of calcium by carbonyl cyanide, p-trifluoromethoxy-phenylhydrazone (FCCP)- and (or) cyanide (CN)-sensitive and insensitive constituents of axoplasm. Known calcium loads imposed on the axon by stimulation produced proportional increments of free axoplasmic calcium. Measurement of increments in ionized calcium as a function of load confirmed earlier reports of buffering in normal and FCCP- and (or) CN-poisoned axons. Measurement of rates of calcium uptake by presumed mitochondria showed little uptake at ambient Ca below 200--400 nM, with sigmoidal rise to about 20--30 mumol/kg axoplasm per min (calculated to be about 200 mmol/kg mitochondrial protein per min) at 50 micrometer, indicating a functional threshold for presumed mitochondrial uptake well above physiological ionized calcium concentration. Treatment of stimulated axons with cyanide, to release calcium from presumed mitochondria, showed that the sensitivity to cyanide decreased progressively with time after stimulation (t 1/2 = 3--10 min) implying transfer of sequestered calcium into a less metabolically labile form.
通过差示吸收光谱法（使用偶氮胂III和安替比林偶氮III）对分离的鱿鱼轴突中的细胞内游离钙离子进行连续无损监测，以研究羰基氰化物、对三氟甲氧基苯腙（FCCP）和（或）氰化物（CN）敏感和不敏感的轴浆成分对钙的摄取情况。刺激施加于轴突的已知钙负荷会使轴浆游离钙按比例增加。测量游离钙离子增加量与负荷的关系，证实了早期关于正常、FCCP和（或）CN中毒轴突中缓冲作用的报道。对假定的线粒体摄取钙的速率进行测量，结果显示在环境钙浓度低于200 - 400 nM时摄取量很少，在50微摩尔时呈S形上升至约20 - 30微摩尔/千克轴浆每分钟（经计算约为200毫摩尔/千克线粒体蛋白每分钟），这表明假定的线粒体摄取的功能阈值远高于生理游离钙浓度。用氰化物处理受刺激的轴突以从假定的线粒体中释放钙，结果表明刺激后对氰化物的敏感性随时间逐渐降低（t1/2 = 3 - 10分钟），这意味着被隔离的钙转移到了代谢活性较低的形式。
