Single channel recordings of calcium-activated potassium channels in the apical membrane of rabbit cortical collecting tubules.

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Abstract
Recordings of single K channels from the apical membrane of rabbit cortical collecting tubule have been achieved using the patch-clamp technique. The conductive properties of the channel were studied in inside/out patches. The slope conductance of the open channel is .apprxeq. 90 pS. The channel is selective to K over Na, with a selectivity ratio of 9:1. Decreasing the Ca concentration of the solution bathing the cytoplasmic face of the patch results in a decrease of the open-channel probability. Decreasing the Ca concentration to .ltoreq. 10 nM completely inhibited channel activity. The channel is also inhibited by Ba in a dose-dependent fashion.