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Gap Junctional Conductance Is a Simple and Sensitive Function of Intracellular pH

D.C. Spray, A. L. Harris and M. V. L. Bennett
Science
New Series, Vol. 211, No. 4483 (Feb. 13, 1981), pp. 712-715
Stable URL: http://www.jstor.org/stable/1685624
Page Count: 4
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Gap Junctional Conductance Is a Simple and Sensitive Function of Intracellular pH
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Abstract

The pH of the cytoplasm (pH$_{i}$) 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 pH$_{i}$ 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 pH$_{i}$ appears to be a cooperative process involving several charged sites. The absence of hysteresis and identity of effects for fast and slow pH$_{i}$ changes implies that protons act directly on the channel macromolecules and not through an intermediate in the cytoplasm.

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