Thallium replaces potassium in activation of the (Na+,K+)-ATPase of rat liver plasma membranes.

The capacity of thallium to substitute for K+ in activation of (Na+,K+)-ATPase of liver plasma membranes was studied. Our results indicate that T1+ can replace K+ in the activation of the (Na+,K+)-ATPase of liver plasma membranes. In the presence of Na+, similar activation is obtained with T1+ concentrations only 1/10 of those of K+. In all other aspects, the (Na+,K+)- and (Na+,T1+)-ATPases were found to be identical.