Application of Cryopreserved Cells to hERG Screening Using a Non-Radioactive Rb + Efflux Assay

The aim of the present study was to test the use of cryopreserved cells for human ether-ago- go (hERG) channel screening. A stable Chinese hamster ovary-K1 cell line expressing hERG channels was used in a non-radioactive Rb⁺ efflux assay for screening hERG channel activity. Cells prepared from normal cultures and following cryopreservation were compared with regard to time course of Rb⁺ efflux response at different concentrations of KCl, overall cell morphology, signal-tonoise assay window, assay robustness, and 50% inhibitory concentration (IC₅₀) of the hERG blocker dofetilide. Our results showed that cryopreserved hERG-expressing cells at 1, 2, and 3 days following plating at different cell densities had no obvious morphological changes in comparison to the growing cells. The assay window, Z' factor, and IC₅₀ of dofetilide were also very similar in all series of cells tested. It was concluded that the cryopreserved hERG cells prepared using the protocol described are as effective as growing hERG cells in the non-radioactive Rb⁺ efflux assay.