(A) Macroscopic current traces obtained from WT Cx32*Cx43E1 unapposed hemichannels after polarizations in 20-mV increments between −90 and 50 mV from a holding potential of 0 mV. The small increase in current level at large positive voltages results from the activation of an endogenous oocyte channel as assessed by recording uninjected oocytes. (B) Macroscopic current traces obtained from an uninjected oocyte illustrating typical endogenous currents present in oocytes obtained from Xenopus 1 frogs in Cs-MES bath solutions. There is variability in the form and magnitude of endogenous currents among oocytes, but in most cases endogenous currents contribute <300 nA.