Inhibition of ROMK S44D mutant expressed in HEK293 cells assessed as inhibition of thallium efflux incubated for 20 mins prior to thallium addition measured after 7 to 12 secs by fluorescence assay
Inhibition of human ROMK channel-mediated 86Rb+ flux expressed in CHO cells at 30 uM after 35 mins by scintillation counting analysis relative to control
Electrophysiology Assay: Block of Kir1.1 (ROMK1) currents was examined by whole cell voltage clamp (Hamill et. al. Pfluegers Archives 391:85-100 (1981)) using the IonWorks.RTM. Quattro automated electrophysiology platform (Molecular Devices, Sunnyvale, Calif.). Chinese hamster ovary cells stably expressing Kir1.1 channels were maintained in T-75 flasks in cell culture media in a humidified 10% CO.sub.2 incubator at 37.degree. C. Prior to an experiment, Kir1.1 expression was induced by overnight incubation with 1 mM sodium butyrate. On the day of the experiment, cells were dissociated with 2.5 ml of Versene.TM. (Invitrogen 15040-066) for approximately 6 minutes at 37.degree. C. and suspended in 10 ml of bath solution containing (in mM): 150 NaCl, 10 KCl, 2.7 CaCl.sub.2, 0.5 MgCl.sub.2, 5 HEPES, pH 7.4. After centrifugation, the cell pellet was resuspended in approximately 4.0 ml of bath solution and placed in the IonWorks.RTM. instrument. The intracellular solution consisted of (in mM): 80 K gluconate, 40 KCl.
Thallium Flux Assay: FluxOR Kit Components (Invitrogen F10017) FluxOR Reagent (Component A) FluxOR Assay Buffer (Component B)-10x Concentrate PowerLoad Concentrate (Component C)-100x Concentrate Probenecid (Component D)-Lyophilized sample is kept at -20 C. Water soluble, 100x after solubilization in 1 ml water. Store at 4 C. FluxOR Chloride-free Buffer (Component E)-5x Concentrate Potassium sulfate (K2SO4) Concentrate (Component F)-125 mM in water. Store at 4 C. Thallium sulfate (Tl2SO4) Concentrate (Component G)-50 mM in water. Store at 4 C. DMSO (dimethyl sulfoxide, Component H)-1 ml (100%) Reagent Preparation- FluxOR Working Solutions 1000x FluxOR Reagent: Reconstitute a vial of component A in 100 ul DMSO; Mix well; Store 10 ul aliquots at -20 C. 1x FluxOR Assay Buffer: Dilute Component B 10-fold with water; Adjust pH to 7.4 with Hepes/NaOH; Filter and store at 4 C.