Curtin N A
Biophys J. 1986 Nov;50(5):837-41. doi: 10.1016/S0006-3495(86)83524-X.
Intracellular pH (pHi) and buffer power of frog muscle were measured using pH-sensitive microelectrodes under conditions used previously in energy balance experiments because pH strongly influences the molar enthalpy change for phosphocreatine splitting, the major net reaction during brief contractions. The extracellular pH (pHe) of HEPES buffered Ringer's solution influenced pHi, but change in pHi developed slowly. Addition or removal of CO2 or NH3 from the extracellular solution caused a rapid change in pHi. The mean buffer power measured with CO2 was 38.4 mmol.l-1.pH unit-1 (+/- SEM 2.1, n = 49) and with NH3 was 36.2 (+/- SEM 5.5, n = 4) at 20-22 degrees C. At 5 degrees C, in experiments with CO2 the mean buffer power was 40.3 (+/- SEM 2.6, n = 3). For pHi values above approximately 7.0, the observed buffer power was greater than that expected from the values in the literature for the histidine content of intracellular proteins, carnosine and inorganic phosphate in the sarcoplasm. The measured pHi values were similar to those assumed in energy balance calculations, but the high measured buffer power suggests that other buffering reactions occur in addition to those included in energy balance calculations.
在先前能量平衡实验所采用的条件下，使用pH敏感微电极测量了青蛙肌肉的细胞内pH值（pHi）和缓冲能力，因为pH强烈影响磷酸肌酸分解的摩尔焓变，而磷酸肌酸分解是短暂收缩过程中的主要净反应。HEPES缓冲林格氏液的细胞外pH值（pHe）影响pHi，但pHi的变化发展缓慢。向细胞外溶液中添加或去除CO₂或NH₃会导致pHi迅速变化。在20 - 22℃时，用CO₂测量的平均缓冲能力为38.4 mmol·l⁻¹·pH单位⁻¹（±标准误2.1，n = 49），用NH₃测量的平均缓冲能力为36.2（±标准误5.5，n = 4）。在5℃时，在使用CO₂的实验中，平均缓冲能力为40.3（±标准误2.6，n = 3）。对于pHi值高于约7.0的情况，观察到的缓冲能力大于根据文献中肌浆内细胞内蛋白质、肌肽和无机磷酸盐的组氨酸含量所预期的值。测量得到的pHi值与能量平衡计算中假设的值相似，但测量得到的高缓冲能力表明，除了能量平衡计算中所包含的缓冲反应外，还发生了其他缓冲反应。
