Figure 4.

Development of a thallium flux assay for Kir2.3. (A) Thallium flux-dependent FluoZin-2 fluorescence recorded from monoclonal Kir2.3 T-REx-HEK-293 cells cultured overnight in absence (−Tet) or presence (+Tet) of Tetracycline. The fluorescence emission was recorded before and after the addition of extracellular thallium (shaded box). (B) Representative traces for changes of Tl⁺-induced FluoZin-2 fluorescence following 20 min pre-treatment of cells with the indicated concentrations of VU573. (C) CRC for VU573-dependent inhibition of Kir2.3 activity. Values are mean ± SEM (n = 3). A fit of the CRC with a single-site four-parameter logistic function yielded IC₅₀ of 4.7.