Vanheel B, de Hemptinne A, Leusen I
J Mol Cell Cardiol. 1985 Jan;17(1):23-9. doi: 10.1016/s0022-2828(85)80089-4.
The influence of external buffering on surface pH (pHs), intracellular pH (pHi) and developed twitch tension was investigated in rabbit and cat papillary muscle. pHs and pHi were measured using single and double-barreled microelectrodes respectively. In 20 mM HEPES buffered solution, steady state pHi is close to that in control CO2/HCO-3 (25 mM HCO-3, 5% CO2) solution. pHs and developed tension also do not differ greatly from their control values. Decreasing the HEPES concentration to 5 mM, at constant external pH, lowers pHs considerably. The surface acidosis is associated with a small intracellular acidification; steady state pHi in 5 mM HEPES is always more acid than that in control CO2/HCO-3. A significant decrease in developed tension is also seen in 5 mM HEPES. Alteration of the superfusion velocity influences pHs only slightly. Stimulation of the muscle at high frequency is shown to increase surface acidification, the extent of which is dependent on the buffer concentration. The conclusion from the present experiments is that in papillary muscle external buffering influences intracellular pH and contraction via its effect on pHs.
研究了外部缓冲对兔和猫乳头肌表面pH值（pHs）、细胞内pH值（pHi）和所产生的收缩张力的影响。分别使用单管和双管微电极测量pHs和pHi。在20 mM HEPES缓冲溶液中，稳态pHi接近对照CO2/HCO-3（25 mM HCO-3，5% CO2）溶液中的pHi。pHs和所产生的张力与对照值也没有很大差异。在外部pH恒定的情况下，将HEPES浓度降至5 mM会显著降低pHs。表面酸中毒伴有轻微的细胞内酸化；5 mM HEPES中的稳态pHi总是比对照CO2/HCO-3中的更酸。在5 mM HEPES中也观察到所产生的张力显著降低。改变灌流速度对pHs的影响很小。高频刺激肌肉会增加表面酸化，其程度取决于缓冲液浓度。本实验的结论是，在乳头肌中，外部缓冲通过对pHs的影响来影响细胞内pH值和收缩。
