Aickin C C, Thomas R C
J Physiol. 1975 Nov;252(3):803-15. doi: 10.1113/jphysiol.1975.sp011171.
The internal pH of crab muscle fibres was measured using recessed-tip pH-sensitive micro-electrodes. Immediately following electrode penetration the mean internal pH was 7-21 +/- 0-02 (S.E. of mean) and the mean membrane potential was -64-9 +/- 0-6 mV (S.E. of mean). If H+ ions were passively distributed across the fibre membrane the internal pH would have been 6-39. 2. The internal pH tended to rise before stabilizing at a mean value of 7-27 +/- 0-02 (S.E. of mean). The difference between immediate and stabilized values is highly significant and suggests acid injury on electrode penetration. 3. Changing the membrane potential or external pH had only small, slow effects on internal pH. 4. External CO2 caused a large and rapid decrease in internal pH. With low concentrations of CO2, the effect was dependent on the initial pH as predicted by the Law of Mass Action. During a long exposure to 2-65% CO2 at pH 7-5, the internal pH returned slowly to its previous value, suggesting active transport of H+ (or OH- or HCO3-) ions across the fibre membrane. 5. The internal buffering power calculated from the response to 2-65% CO2 was 47-3 +/- 2-8 slykes (m-equiv H+/pH unit per l.) (S.E. of mean).
使用凹头pH敏感微电极测量蟹肌纤维的内部pH值。电极刺入后，内部pH值的平均值立即为7.21±0.02（平均值的标准误），平均膜电位为-64.9±0.6 mV（平均值的标准误）。如果H⁺离子在纤维膜上被动分布，内部pH值应为6.39。2. 内部pH值在稳定在平均值7.27±0.02（平均值的标准误）之前有上升趋势。立即值与稳定值之间的差异非常显著，表明电极刺入时存在酸损伤。3. 改变膜电位或外部pH值对内部pH值的影响很小且缓慢。4. 外部CO₂导致内部pH值大幅快速下降。对于低浓度的CO₂，其影响取决于质量作用定律预测的初始pH值。在pH值为7.5的条件下长时间暴露于2.65%的CO₂时，内部pH值会缓慢恢复到先前的值，这表明H⁺（或OH⁻或HCO₃⁻）离子在纤维膜上进行主动转运。5. 根据对2.65% CO₂的响应计算出的内部缓冲能力为47.3±2.8 slykes（每升m当量H⁺/pH单位）（平均值的标准误）。
