Effect of external potassium concentrations, insulin and lactate on frog muscle potassium and respiratory rate

¹ Department of Biochemistry, University of Toronto, Toronto, Canada

In Ringer's solution containing 10 mEq K/l., frog muscles consumed oxygen at 20°C at rates ranging from 88 (summer frogs) to 128 (winter frogs) cu mm/gm/hr. These rates, which were three to four times higher than those at 2 and 6 mEq K/l., continued to rise for at least 6 hours, although the muscles had previously been soaked at 5°C in the type of Ringer's in which they respired. Addition of lactate increased the respiratory rate at all K concentrations studied. When insulin was present a marked additional stimulation was observed at 2 and 6 mEq K/l., which was changed to an inhibition at 10 mEq/l. Potassium analyses of all of the environmental fluids and of the muscles (144 of each) demonstrated a slight K loss from control muscles which was reduced or abolished by lactate. Insulin, however, either with or without added lactate, abolished the K loss and induced an appreciable K uptake. This K gain occurred regardless of the effect of insulin on the respiratory rate. Denaturation of the insulin abolished all of its effect. Seasonal differences were noted.