Ionic bases of resting and action potentials in salivary gland acinar cells of the snail Helisoma.

Values for resting and action potentials of Helisoma salivary gland cells are much the same as in most neurones and muscle cells. The resting potential is primarily due to the distribution of potassium ions across the membrane, with a small contribution by an electrogenic sodium pump. Estimated values for intracellular potassium concentration and the relative membrane permeabilities to sodium and potassium ions correspond to similar estimates in other excitable tissues. The inward current of the salivary gland action potential is carried predominantly by calcium ions and possibly serves as a mechanism of calcium entry for stimulus-secretion coupling.