Modification of the electrical properties of frog sartorius muscles by salts of L-aspartic acid

Abstract

Resting membrane potentials and action potentials of frog sartorius muscle fibers were measured using intracellular glass microelectrodes. L-K-aspartate or L-Na-aspartate was capable of repolarizing the muscle cells which had been depolarized by reducing intracellular potassium or by elevating the potassium in the bathing medium. The repolarization (6–10 mV) was accompanied by an equivalent increase in the negative after-potential (N.A.P.) without altering other action potential parameters. The response occured in either isotonic or hypertonic Ringer's solution. Possible mechanisms which could produce hyperpolarization are examined and it is concluded that the repolarization may be associated with increased potassium retention which occurs in the presence of aspartic acid.