[3H]Dofetilide binding in SHSY5Y and HEK293 cells expressing a HERG-like K+ channel?

The pharmacological characteristics of [H-3]dofetilide binding in SHSY5Y, HEK293 and CHO-K1 cells were examined, and in parallel whole cell recordings used to characterise HERG-like K+ currents. Dofetilide affinity was similar in the human cell lines, SHSY5Y (K-d = 99.6 nM) and HEK293 ( K-d = 102.9 nM), but 10 times lower in CHO-K1 cells (K-d = 1200 nM). In contrast, clofilium and E4031 had a similar affinity in all three cell lines, whereas WAY 123,398 had no effect. Electrophysiological studies showed that SHSY5Y cells contained a HERG-like K+ current blocked by application of dofetilide to either side of the membrane. Block was faster when dofetilide was applied intracellularly. In contrast, HEK293 and CHO-K1 cells contained no such current, despite the presence of a partial cDNA for HERG in the former. That [H-3]dofetilide is specific for I-Kr/HERG may be questionable, as HEK293 and CHO-K1 cells contain no such functional K+ current. (C) 2001 Elsevier Science B.V. All rights reserved.