Whole-cell patch-clamp recording mode was used to study the action mechanism of La^3^+ on rat ventricular myocytes potassium channels. The Ca^2^+-independent voltage-activated outward K^+ current was activated by the depolarizing pulse in enzymatically isolated rat ventricular myocytes. When 10 μmol/L La^3^+ was added to the bath solution, the Ca^2^+-independent voltage-activated outward K^+ current was distinctly suppressed. It implies that there may exist one or more binding-sites in potassium channels for La^3^+.

Key words: LANTHANUM ION, MOLECULAR SCIENCE, TOXICOLOGY, RARE ELEMENT