The Role of Calcium tons in the Acceleration of Resting Muscle Glycolysis by Extracellular Potassium

The activation of the glycolysis of resting muscle by increased extracellular potassium is dependent upon the simultaneous presence of calcium, but not of sodium ions. This regulation of metabolism by a membrane characteristic seems to act upon an early link in the glycolytic enzyme chain. The classical investigations of Overton (1902, 1904) have shown that, while an isolated muscle maintains its irritability in balanced ion media, replacement of the sodium by a non-electrolyte, or partial replacement by potassium, leads to a loss in excitability. Later studies, emphasizing especially the potassium effect (cf. Duli~re and Horton (1929); Horton (1930)) have furthermore demonstrated that in such media there is a significant increase in resting metabolism (Fenn (1930) ; Hegnauer, Fenn, and Cobb (1934) ; Tipton (1936) ; Solandt (1936a, b); Smith and Solandt (1938); Hill and Howarth (1957)). The transfer of a muscle into a high K medium may also lead to initial twitching or contracture (cf. Hodgkin and Horowiez (1957)), but the metabolic effects are of considerable magnitude and of much longer duration, and are held to be independent of any small initial contractile activity (e.g. Hill and Howar th (1957)). I t has become accepted to ascribe this metabolic activation to a partial depolarization of the membrane, too small, or too slowly established, to elicit contraction. Clearly, this regulation of metabolic intensity by a membrane property is of considerable interest for the understanding of the link between excitation and response. This investigation was supported by research grant No. H-3067 of the National Heart Institute, National Institutes of Health, Bethesda, Maryland. This work was done during the tenure of research fellowships from the National Association for Infantile Paralysis and the Southern California Permanente Medical Group. Received for publication, April l l , 1960.