Abboud C N, Scully S P, Lichtman A H, Brennan J K, Segel G B
J Cell Physiol. 1985 Jan;122(1):64-72. doi: 10.1002/jcp.1041220111.
The extracellular ionized calcium and magnesium requirements for lectin-induced lymphocyte DNA synthesis were measured in a serum-free system. The use of this system permitted measurements of the ionized calcium and magnesium concentrations with ion-selective electrodes. Maximal DNA synthesis was observed at 270 microM ionized calcium and at 100 microM ionized magnesium in phytohemagglutinin-treated lymphocytes. Lymphocyte DNA synthesis was much more sensitive to reduction of external ionized calcium than to reduction of ionized magnesium. In calcium-free medium (ionized calcium 25 microM), DNA synthesis was reduced by 90%, but in magnesium-free medium (ionized magnesium concentration 7 microM) DNA synthesis was reduced by only 30%. Fifty percent of DNA synthesis stimulated by phytohemagglutinin (PHA) and concanavalin A (Con A) was observed at external ionized calcium concentrations of 97 and 43 microM, respectively. When lymphocytes were stimulated with PHA and the external calcium was chelated with EGTA, 50% inhibition of DNA synthesis was observed at 98 microM ionized calcium. This value agreed well with the free calcium required for PHA activation of DNA synthesis (97 microM). Cytoplasmic calcium, measured with the fluorescent probe Quin 2, increased following lectin exposure if the extracellular ionized calcium concentration was greater than 80 microM. No increase in cytoplasmic calcium could be detected in lectin-treated lymphocytes below 80 microM extracellular ionized calcium, although substantial DNA synthesis was sustained.
在无血清体系中测定了凝集素诱导淋巴细胞DNA合成所需的细胞外游离钙和镁。使用该体系可通过离子选择电极测量游离钙和镁的浓度。在植物血凝素处理的淋巴细胞中，当游离钙浓度为270微摩尔/升、游离镁浓度为100微摩尔/升时观察到最大DNA合成。淋巴细胞DNA合成对外源游离钙降低的敏感性远高于对游离镁降低的敏感性。在无钙培养基（游离钙25微摩尔/升）中，DNA合成降低了90%，但在无镁培养基（游离镁浓度7微摩尔/升）中，DNA合成仅降低了30%。分别在游离钙浓度为97和43微摩尔/升时观察到植物血凝素（PHA）和伴刀豆球蛋白A（Con A）刺激的DNA合成的50%。当用PHA刺激淋巴细胞且外源钙用乙二醇双四乙酸（EGTA）螯合时，在游离钙浓度为98微摩尔/升时观察到DNA合成受到50%的抑制。该值与PHA激活DNA合成所需的游离钙（97微摩尔/升）非常吻合。如果细胞外游离钙浓度大于80微摩尔/升，用荧光探针喹啉2测量的细胞质钙在凝集素暴露后会增加。在细胞外游离钙低于80微摩尔/升的凝集素处理的淋巴细胞中，虽然维持了大量的DNA合成，但未检测到细胞质钙增加。
