Gap junctional conductance is a simple and sensitive function of intracellular pH.
Gap junctional conductance is a simple and sensitive function of intracellular pH.
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间隙连接电导是细胞内 pH 值的简单而敏感的函数。
作者：
D. Spray;Andrew L. Harris;Michael V. L. Bennett
用pH敏感微电极测定了两栖类（Ambystoma）和硬骨鱼（Fundulus）胚胎卵裂期卵裂球的细胞质pH值（pHt）约为7.7。在电张力偶联的细胞对中，连接电导由于细胞质的酸化而迅速而可逆地降低。结电导和pHi之间的关系对于pH的增加和减少是相同的，并且在很宽的范围内与变化率无关。当K = 50 nM (pK = 7.3), n = 4 ~ 5时，采用Hill曲线拟合关系良好。在低pHi下，间隙结通道的闭合似乎是一个涉及多个带电位点的合作过程。快速和缓慢pHi变化的不存在滞后性和效应的同一性意味着质子直接作用于通道大分子，而不是通过细胞质中的中间体。
The pH of the cytoplasm (pHt) measured with pH-sensitive microelectrodes in cleavage-stage blastomeres of amphibian (Ambystoma) and teleost (Fundulus) embryos is about 7.7. In electrotonically coupled cell pairs, junctional conductance is rapidly and reversibly reduced by acidification of the cytoplasm. The relation between junctional conductance and pHi is the same for increasing and decreasing pH and is independent of the rate of change over a wide range. The relation is well fitted by a Hill curve with K = 50 nM (pK = 7.3) and n = 4 to 5. The closure of gap junction channels at low pHi appears to be a cooperative process involving several charged sites. The absence of hysteresis and identity of effects for fast and slow pHi changes implies that protons act directly on the channel macromolecules and not through an intermediate in the cytoplasm.