Thallium and cesium in muscle cells compete for the adsorption sites normally occupied by K+.

It was shown that Tl+ can stoichiometrically displace K+ in frog muscle cells. This displacement is independent of the function of cell membrane and postulated pumps and of a macroscopic electric charge or Donnan effect. It follows that Cs+ and Tl+ compete for the adsorption sites normally occupied by K+. On this basis, the association-induction hypothesis predicts that Cs+ and Tl+, like K+, should be primarily localized in the A-band of the muscle myofibrils.