The gating of human red cell Ca2(+)-activated K(+)-channels is strongly affected by the permeant cation species.

Using inside-out patches, the effect of various permeant cations on the gating behaviour of the human red cell Ca2(+)-activated K(+)-channel was examined. For symmetric solutions the dwell time histograms indicated two shut and two open states. Mean open times as well as the open-state probability were affected by the permeant cation species: Rb+ stabilised the channel in the open configuration, whereas NH4+ had a destabilising effect. Intermediate stability was obtained in K+ solutions. Bi-ionic experiments indicated that the gating was influenced by the ion species occupying the channel, rather than by ions bound to external modifier sites.