Rubidium Flux

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Rubidium Flux
Authored by: Paul Taylor, Boehringer Ingleheim Inc.

This technique is an alternative to patch clamp electrophysiology for measuring changes in membrane potential upon activation of ion channels.^[1]^[2] Rubidium is similar to K⁺ in its capability of penetrating ion channels and, because of its absence in eukaryotic cells, avoids the possibility of endogenously produced false signals. Cells under study have their culturing buffer containing K⁺ exchanged out with a buffer containing Rb⁺ which initiates a cell-loading phase. Following the loading stage, excess Rb⁺ is washed away in preparation for ion channel activation. This is accomplished either by adding a depolarizing concentration of KCl (voltage-gated) or an appropriate ligand (ligand-gated). Cell supernatants containing effluxed rubidium are then analyzed using atomic absorption spectrometry (AAS) and instrumentation has been developed that allows throughputs of up to 60,000 samples per day using 384-well plates.