Measurements of single-channel currents in the membrane of isolated cells: ATP-dependence of K+-channels.

Single-channel currents in ventricular cells of guinea-pig hearts were recorded by the patch-clamp technique. An inwardly rectifying K+-current was found in cell-attached membrane patches. Patches could be isolated from the cell exposing the cytoplasmic face of the membrane directly to the bathing solution. After isolation, the same current as in cell-attached patches was seen if the bath contained 4 mM ATP. Without ATP, this current disappeared and another channel of larger conductance and different kinetics was activated. Currents through the latter channel were also seen in cell-attached patches after poisoning the cells by DNP. It is suggested that the ATP-dependence of the observed membrane channels mediates the increase of potassium conductance after metabolic inhibition.