DEPOLARIZATION-INDUCED RB-86(+) EFFLUX IN CHO CELLS EXPRESSING A RECOMBINANT POTASSIUM CHANNEL

Cells expressing a recombinant human voltage-activated potassium chann el (K-channel), Kv1.5, have been used in a functional assay that measu res depolarization-stimulated Rb-86(+) efflux as an indicator of K-cha nnel function. Neither untransfected nor vector-transfected cells disp lay measurable Rb-86(+) efflux under depolarizing conditions. The depo larization-induced Rb-86(+) efflux is blocked by standard K-channel bl ockers quinine, il -aminopyridine and 3,4-diaminopyridine, but not by tetraethylammonium, quinidine, glibenclamide, or several peptide toxin s. The pharmacological profile of the recombinant system reflects that reported for the channel in its native state. In such a system with n o observable endogenous background, analysis of recombinant K-channel subtypes allows rapid assessment of pharmacological agents with isofor m selectivity and specificity. Inclusion of compounds of unknown activ ity in an assay such as this could identify agents capable of modulati ng specific K-channel isoforms. Development of this high through-put a ssay system for the study of specific isoforms is a critical step in t he identification and development of drugs that affect the desired tar get tissues with predictable pharmacology and minimal side effects due to nonselective K-channel interaction.