Ionic basis of the resting potential of submucosal arterioles in the ileum of the guinea‐pig.

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Abstract
The changes in the resting membrane potential of arterioles produced by rapid and brief changes in external ionic concentrations were measured. The resting membrane potential was insensitive to changes in the external concentrations of both Na and Cl ions but sensitive to changes in the external concentration of K ions. Increasing the external concentrations of K ions produced depolarizations that were well described by the Nernst equation. Decreased external concentrations of K ions produced membrane depolarizations which appeared to result not from inhibition of an electrogenic Na pump but rather from a change in the resting conductance of the arteriolar membrane to K ions. Ouabain caused both membrane depolarization and an increase in membrane resistance. At rest, arteriolar smooth muscle is permeant predominantly to K ions, with only small contributions from Cl and Na ions. No evidence was obtained which would support the idea that an appreciable proportion of the resting membrane potential depended upon current flow from an electrogenic Na pump.