Gap junctional conductance: comparison of sensitivities to H and Ca ions

One cytoplasmic aspect of the junctional membrane between coupled pairs of Fundulus blastomeres was perfused with solutions of known H and Ca ion concentrations. Conductance of junctional membrane was decreased by either ion. The sensitivity to H ions was about 10,000 times greater than that to Ca ions. The results suggest that junctional conductance can be modulated by changes in H ion concentration near physiological pH, but that unphysiologically high concentrations of Ca ion, such as would be reached only on cell death, are required for comparable changes in junctional conductance.