Inward-rectifying channels in isolated patches of the heart cell membrane: ATP-dependence and comparison with cell-attached patches

摘要

Inward rectifying potassium single-channel currents were studied in the membrane of guinea pig cardiac myocytes. In isolated inside-out patches two different channels were observed: a channel of 25 pS conductance (K+o=147 mM,T=21° C), if the solution at the cytoplasmic face of the patch contained 4 mM ATP and a channel of 80 pS conductance without ATP. The 25-pS-channel was also regularly seen in cell-attached patches (Sakmann and Trube 1984a, b), but the 80-pS-channel appeared only after inhibiting cellular metabolism by DNP. The percentage of time which the 25-pS-channel spent in the open state was 3.3 times larger in isolated patches compared to cell-attached patches. However, both types of single channel currents disappeared several minutes after the isolation of the patches