Functional analysis of native and recombinant ion channels using a high-capacity nonradioactive rubidium efflux assay

A nonradioactive cell-based rubidium (Rb+) efflux assay for functional anal ysis of native and recombinant ion channels has been developed. Cells are f irst loaded with rubidium, a tracer for potassium, and after channel activa tion, rubidium distribution between intracellular and extracellular space i s determined by atomic absorption spectroscopy. The relative amount of rubi dium in the cell supernatant is a direct measure of channel activity. The b road utility of the method is demonstrated by analysis of a range of differ ent ion channels. Ligand-gated ion channels like nicotinic acetylcholine re ceptors and purinergic P2X receptors were studied in native PC-12 cells, Ca lcium-activated potassium channels were analyzed in native (small-conductan ce calcium-activated potassium channel, SKCa) as well as recombinant cell l ines (large-conductance calcium-activated potassium channel, BKCa). Also re combinant voltage-gated potassium channels (Kv1.1, Kv1.4) were amenable to this functional analysis. The method is particularly useful for identificat ion of ion channel modulators in drug discovery since it allows functional analysis with high capacity, (C) 1999 Academic Press.