The effect of potassium on the metabolism of surviving muscle tissue.

The following experiments were undertaken in order to determine whether the pronounced effect of potassium on the contractile process in skeletal and cardiac muscle is associated with changes of metabolism, as indicated by variations in the rate of acid production.

Isolated frog tissues were used in all the experiments and their “normal” rate of acid production was determined in Ringer's solution before treating them with potassium. The Ringer's solution consisted of a mixture of the three chlorides, in the usual concentration for cold-blooded tissues, and the potassium effect was obtained by immersing the muscle in an isotonic solution of potassium chloride. Precaution was taken to have the Ringer's and potassium chloride solutions of the same pH and buffer capacity. The experiments were carried out at various room temperatures, but never did the temperature vary significantly during any one experiment. The experiments fall into three classes, as follows:

1. The effect of potassium on the total acid production of skeletal muscle. Sartorius muscles were used in these experiments and their rate of total acid production was measured by the indicator method of Haas, 1 using phenol red as indicator. Determinations were made of the time, in seconds, required by a muscle to produce sufficient acid to cause an increase in the acidity of the solution it was in from pH 7.381 to pH 7.168. Each determination was made with the muscle immersed in 2.5 cc. of solution (Ringer or KC1) in a hard-glass test tube of 3 cc. capacity, stoppered with a paraffined cork. At least two determinations were made of the rate of acid production in Ringer solution, in order to establish the “normal”, before treating the muscle with potassium; it was then immersed, without any delay, in isotonic potassium chloride solution, previously adjusted to the same pH and buffer capacity as the Ringer.