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Abstract

To obtain further insight into electrogenic steps of the Na⁺/K⁺-pump cycle, current transients can be analysed that result from the perturbance of a steady-state distribution by application of a voltage pulse. Recently a giant patch method was developed (2,4) that allowed detection of pump-generated membrane currents in inside-out patches of cardiac cells and Xenopus oocytes. Application of the two-electrode voltage-clamp method is questionable in this respect since space clamp cannot be achieved within the first milliseconds. A drawback of the giant-patch method was that outside-out orientation could be obtained only occasionally. Here we apply a modified procedure that allows routinely also the formation of outside-out membrane patches of oocytes with diameters of up to 45 μm.