2',7'-Bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) is frequently used for fluorometric determination of intracellular pH (pHi) and its metabolic changes. Studies of BCECF-loaded platelets have reported different pHi values in the range of 6.98 to 7.35, despite the use of the same probe. It is now shown that intracellular BCECF (BCECFi) content affects pHi, and that its over-loading, leads to significantly lower pHi. Different pHi values can be reproduced by changing BCECFi, as reflected by fluorescence intensity. The major loading factors are: the concentration of the probe parent compound, BCECF acetoxymethyl ester (AM), and whether this ester is partly hydrolyzed externally when applied in plasma. When least affected by BCECF, platelet pHi is 7.34. High BCECFi does not affect ATP content, buffer capacity, activation of Na+/H+ exchange by protein kinase C (PKC) and basal PKC activity. On the other hand high BCECFi does inhibit the Na+/H+ exchange rate by over 50%. Since the Na+/H+ exchange strongly affects platelets pHi, it is proposed that this inhibition accounts, at least partly, for the lowered pHi in BCECF over-loaded platelets.

中文翻译：

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BCECF对人血小板细胞内pH的影响。

2'，7'-双-（2-羧乙基）-5-（和-6）-羧基荧光素（BCECF）通常用于荧光测定细胞内pH（pHi）及其代谢变化。尽管使用相同的探针，但加载BCECF的血小板的研究报告了pHi值在6.98至7.35范围内的不同值。现在表明，细胞内BCECF（BCECFi）含量会影响pHi，并且其超载会导致pHi大大降低。通过改变BCECFi可以再现不同的pHi值，如荧光强度所反映。主要的上样因子是：探针母体化合物BCECF乙酰氧基甲基酯（AM）的浓度，以及在血浆中应用时该酯是否部分水解。当受BCECF影响最小时，血小板pHi为7.34。高BCECFi不会影响ATP含量，缓冲液容量，蛋白激酶C（PKC）激活Na + / H +交换和基础PKC活性。另一方面，高的BCECFi确实抑制了Na + / H +交换率超过50％。由于Na + / H +交换强烈影响血小板pHi，因此提出这种抑制作用至少部分是由于BCECF超负荷血小板中pHi降低所致。