Resting potential dependency on external potassium in Amphioxus muscle

¹ Subcommittee on Biophysics, Columbia University, New York City

The resting potential of Amphioxus muscle was determined by using an internal micropipet electrode. The effect of external potassium concentration was studied. From the curvature of the semilogarithmic plot of membrane potential versus external potassium concentration, an estimate can be made of the relative permeability of the membrane (in the resting state) to Na⁺ and K⁺. The permeability to sodium is 0.03 of the permeability to potassium. Structural features which may be responsible for this permeability difference are noted.

Key Words: sarcoplasmic reticulum • membrane permeability

Submitted on August 18, 1964