Rubidium and caesium entry, and cation interaction in frog skeletal muscle

Abstract

Listen

Translate article

Rb and Cs uptake by frog sartorius muscle was measured and the interaction between K, Rb, and Cs studied. Uptake of Rb from various mixtures of Rb and Na salts and the uptake of Cs from various mixtures of Cs and Na salts fell along single curves for a given temperature when plotted against a function of concentration x time of exposure. The relative exchangeabilities of K for K, Rb, and Cs, respectively, were 1:0.2:0.04. Uptakes of Rb or Cs from mixtures with K or with each other are shown to be consistent with predictions. Entry of Rb into previously K-depleted muscles, so that Na is displaced by Rb, was faster than the interchange of Rb with the muscle K. Uptake of labeled K from mixtures with Rb or Cs followed a course consistent with the hypothesis that when Rb or Cs has entered the ion-exchange region the K exchange is slowed down. In the case of Rb + K mixtures, the K exchange ultimately fell to the same rate as holds for Rb-K interchange, but Cs took longer to exert its full inhibitory effect. Experiments in which the internal-external resistance of fibers from a pair of muscles were measured,more » in solutions containing respectively 3 mm K or Rb with Na methyl sulfate, showed that the values in the Rb solution were 2 to 4 times those in the K solution. Experiments also indicated that the Cl exchange process follows the same pattern as that described for the cations. (TCO)« less