Characteristics of the anion channel in the sino‐atrial node cell of the rabbit.

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Abstract
The anion permeability of the sino-atrial node cell membrane was determined by substituting various anions for Cl and observing the resultant transient changes in membrane potential. The permeability sequence was in the following order: thiocyanate > NO3 > I > Br > Cl > acetate. The membrane resistance in Cl solution was compared with that in various anion solutions by the voltage-clamp method. The conductance sequence for the sino-atrial node cell membrane was observed to be the same as the permeability sequence. The potential generated by the Na-K pump was partly short-circuited in normal bathing solution; the pump could be responsible in part for the generation of the sino-atrial node resting membrane potential. When Cl was replaced by acetate, a less permeable ion, the inward-going rectification disappeared. The inward-going rectification might be due partly to a time- and voltage-dependent Cl current.