ACTION OF K-STROPHANTHIN ON POTASSIUM LEAKAGE FROM FROG SARTORIUS MUSCLE

¹ Department of Pharmacology, University of Berne, Switzerland

The potassium loss of frog sartorius muscle into potassium-free Ringer, which is exchanged regularly, was measured with a flame photometer.

The resting muscle loses significantly more potassium when strophanthin 10^-5 is added to the Ringer, and the loss is still higher in DNP 0.2 mM. There is no difference of potassium loss between a muscle in DNP and a muscle in DNP plus strophanthin.

A muscle twitching at a rate of 30 per minute loses more potassium than the resting muscle. The loss is not significantly increased by strophanthin 10^-5, but is higher in DNP 0.2 mM. Adding strophanthin to the muscle twitching in DNP reduces the overall potassium loss significantly, when compared to the loss in DNP alone.

Arguments are advanced in favor of the hypothesis that strophanthin blocks the sodium-potassium-pump in resting muscle, but has an additional retarding effect on potassium outflow during the falling phase of an action potential in the twitching muscle.