Rubidium flux assays

Rubidium exhibits a very high flux through potassium ion channels. Upon depolarization, this flux can be quantified as a measure of channel integrity (Tang et al. 2001 Chang et al. 2002). Fluorometric assays have been developed that can detect drug-induced effects on hERG channels. 

Cheng CS, Alderman D, Kwash J, Dessaint J, Patel R, Lescoe MD, Kinrade MB, Yu W (2002) A high-throughput HERG 

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Each of these techniques can give quite different hERG IC50 values for the same compound. Eor example, terfenadine s IC50 has been measured at 30 nM in the patch-clamp assay, 4.8 pM in the rubidium flux assay, and 500 nM in a binding assay. Needless to say, numbers from different assays, different cells, or different labs for that matter, can t be directly compared. 

The assays are based on the flux of ions through channels such as rubidium (Rb+) or thallium (TI+) [15-17] ions through the hERG channel and lithium (Li+) ions through the Navi.5 [18]. 

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