Possible role of Ca ions in the resting metabolism of frog sartorius muscle during potassium depolarization

Oxygen consumption and Ca exchangeability at different levels of potassium depolarization were studied in frog sartorius muscle. It was found that the changes in oxygen consumption parallel the changes in Ca exchangeability. Procaine (10−3 M) and CaCl2 (2.10−2 M) suppressed both extra oxygen consumption and Ca exchangeability at low values of depolarization. At higher values of depolarization procaine and CaCl2 differed in their action. Procaine favored inhibition of these processes, CaCl2 caused their activation. The effects of these compounds was not a result of a change in the membrane potential, since their effect on potassium depolarization was found to be small. Relations between oxygen consumption and Ca exchangeability similar to those observed at potassium depolarization seem to exist under conditions where caffeine was applied. It is proposed that the extra oxygen consumption caused by potassium depolarization or on application of caffeine and unaccompanied by mechanical changes is related to the release of Ca from its bound form. Oxygen consumption in isotonic sucrose solution was also studied, but some different data from the above were obtained.