Sodium, potassium, and chloride in frog stomach muscle

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Abstract
In freshly excised stomach muscles of Rana temporaria total Na was found to be 40.2 ± 6.1 mEq/kg wet wt. Total K was 66.5 ± 4.8 and total Cl was 33.9 ± 3.9 mEq/kg. Total water content was 805 ± 16 g/kg and inulin space was 341 ± 52 ml/kg. The average intrafiber concentrations calculated from these data were 10 mEq Na, 141.5 mEq K, and 18 mEq Cl/ liter fiber water. In muscles immersed overnight at 5 C in Ringer's solutions containing various amounts of KCl, total muscle Cl was a direct linear function of external KCl. When the external KCl concentration was less than 20 mm/liter, muscle K decreased on immersion. Increasing the external KCl from 20 to 40 mm/liter resulted in a sharp increase in muscle K. Further increasing external KCl from 40 to 80 mm/liter had relatively little effect on total muscle K. The Na content of these muscles was in all cases greater than that of freshly excised muscles. Muscles immersed overnight in the cold in K-free solutions gained Na and lost K. On reimmersion at room temperature in solutions containing KCl there was a net loss of Na from and a net gain of K by the fibers. The amount of K taken up was a function of the external KCl concentration. Na loss and K accumulation were inhibited by ouabain and by iodoacetate.