Heavy water inhibition of alkali cation transport across the muscle membrane. II. A comparison of the action of D20 and ouabain on the sodium efflux and rubidium influx in magnesium media

The action of heavy water and ouabain on sodium effluxes and rubidium influxes has been measured and compared in frog muscles (m. sartorius, R. temporaria). Approximately half of muscle sodium was substituted by lithium by preliminary incubation in mixed sodium-lithium media. The ratio of the ouabain-sensitive parts of rubidium influx and sodium efflux is 7.3:10.5, and that of D2O-sensitive parts of corresponding parameters is 7.5:11.3. A conclusion is made that D2O-effect on the Na, K-ATPase system of muscles under investigation resembles ouabain-effect on sodium effluxes as well as on rubidium influxes.