[Heavy water inhibition of the transport of alkaline cations across the muscle membrane. I. A comparison of different types of sodium transfer].

The sodium efflux from the frog sartorius muscle into the media of different ion composition, prepared with ordinary and heavy water, was measured by radiotracer and flame-emission techniques. About the half of the sodium in muscles was substituted for lithium. The ouabain-sensitive, as well as external potassium- and external sodium-dependent components of the efflux were found to be totally inhibited in D2O, whereas the residual efflux observed in sodium- and potassium-free magnesium medium was diminished in D2O only by one half. A conclusion is made that the decrease in sodium efflux in D2O is due to the inhibition of sodium transfer through the Na, K-ATPase transport system.