1. The effect of altering the extracellular pH (pHo) on the electrical activity of the isolated rabbit sino-atrial (s.a.) node was studied using the two-micro-electrode voltage-clamp technique. 2. Alkalinization of the perfusate increased the maximum rate of rise and amplitude of the nodal action potential, and also the frequency of spontaneous beating of the s.a. node; acidification produced opposite effects. 3. A change in the extracellular pH from a value of 6.5 to 8.5 caused increases of the maximal conductance for both the slow inward current and the steady-state outward current systems without affecting the gating processes of the channels. 4. H+ could modify the electrical activity of s.a. nodal cells, not through altering the membrane surface potential but through the protonation of the ionic channels themselves. From the titration curves, the apparent pKa values for the slow inward current and the steady-state outward current were estimated to be 6.4 and 6.0, respectively.
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机译:1.使用双微电极电压钳技术研究了改变细胞外pH(pHo)对离体兔窦房(s.a.)节点电活动的影响。 2.灌注液的碱化增加了结节动作电位的最大上升速率和幅度,也增加了s.a的自发搏动频率。节点;酸化产生相反的作用。 3.细胞外pH从6.5更改为8.5会导致缓慢的内向电流系统和稳态的外向电流系统的最大电导增加,而不会影响通道的门控过程。 4. H +可以改变s.a.的电活性。节点细胞,不是通过改变膜表面电位,而是通过离子通道本身的质子化。根据滴定曲线,缓慢的内向电流和稳态的外向电流的表观pKa值分别估计为6.4和6.0。
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