The potassium uptake and rate of oxygen consumption of isolated frog skeletal muscle in the presence of insulin and lactate.

Insulin (5.0 × 10−2 units per ml.) and lactate (5.0 × 10−3 M) caused an uptake of potassium by intact frog skeletal muscles in vitro, and a concomitant loss of potassium from the medium surrounding the muscles; this fluid was Ringer's solution containing 2.1 meq. of potassium per liter. Thus a movement of potassium against a high concentration gradient has been demonstrated. In general, the conditions under which potassium uptake occurred stimulated the oxygen consumption of the muscles. Monoiodoacetic acid (2.5 × 10−4 M) abolished the effect of insulin on the potassium uptake and greatly reduced its effect on the oxygen consumption.