THE RELATION BETWEEN AMINO ACIDS AND POTASSIUM IN ISOLATED RAT MUSCLE*

Abstract

An intact rat diaphragm preparation was used in this study. Cationic amino acids markedly decrease the steady-state K content of rat skeletal muscle in vitro. Some neutral amino acids have a similar but much less marked effect. Anionic amino acids have no effect. Over the range of external K concentrations of 1 to 9 mEq per L, the net loss of muscle K caused by lysine is inversely related to external K concentration. The K lost from muscle is replaced by equivalent amounts of lysine. Intracellular NA and chloride concentrations are essentially unchanged. The extracellular concentration of cationic amino acids is an important factor influencing the K equilibrium of skeletal muscle in the rat. The mechanism by which amino acids exert their effect is not clear, but it seems unlikely that they compete with K at the cell surface for entry.