Depolarization-induced 86Rb+ efflux in CHO cells expressing a recombinant potassium channel.

Cells expressing a recombinant human voltage-activated potassium channel (K-channel), Kv1.5, have been used in a functional assay that measures depolarization-stimulated 86Rb+ efflux as an indicator of K-channel function. Neither untransfected nor vector-transfected cells display measurable 86Rb+ efflux under depolarizing conditions. The depolarization-induced 86Rb+ efflux is blocked by standard K-channel blockers quinine, 4-aminopyridine and 3,4-diaminopyridine, but not by tetraethylammonium, quinidine, glibenclamide, or several peptide toxins. The pharmacological profile of the recombinant system reflects that reported for the channel in its native state. In such a system with no observable endogenous background, analysis of recombinant K-channel subtypes allows rapid assessment of pharmacological agents with isoform selectivity and specificity. Inclusion of compounds of unknown activity in an assay such as this could identify agents capable of modulating specific K-channel isoforms. Development of this high through-put assay system for the study of specific isoforms is a critical step in the identification and development of drugs that affect the desired target tissues with predictable pharmacology and minimal side effects due to nonselective K-channel interaction.