Functional and pharmacological properties of canine ERG potassium channels

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 284; no. 1; p. H256
• Main Authors: Wang, Jixin, Della Penna, Kimberly, Wang, Hao, Karczewski, Jerzy, Connolly, Thomas M, Koblan, Kenneth S, Bennett, Paul B, Salata, Joseph J
• Format: Journal Article
• Language: English
• Published: United States 01-01-2003
• Subjects: Animals; Benzopyrans - metabolism; Benzopyrans - pharmacology; Binding, Competitive; Blotting, Western; Cell Line; Dogs - physiology; Electric Conductivity; ERG1 Potassium Channel; Ether-A-Go-Go Potassium Channels; Humans; Immunologic Techniques; Ion Channel Gating; Kinetics; Patch-Clamp Techniques; Piperidines - metabolism; Piperidines - pharmacology; Potassium - metabolism; Potassium Channel Blockers - pharmacology; Potassium Channels - drug effects; Potassium Channels - physiology; Potassium Channels, Voltage-Gated; Staining and Labeling; Temperature
• ISSN: 0363-6135
• DOI: 10.1152/ajpheart.00220.2002

We established HEK-293 cell lines that stably express functional canine ether-à-go-go-related gene (cERG) K(+) channels and examined their biophysical and pharmacological properties with whole cell patch clamp and (35)S-labeled MK-499 ([(35)S]MK-499) binding displacement. Functionally, cERG current had the hallmarks of cardiac delayed rectifier K(+) current (I(Kr)). Channel opening was time- and voltage dependent with threshold near -40 mV. The half-maximum activation voltage was -7.8 +/- 2.4 mV at 23 degrees C, shifting to -31.9 +/- 1.2 mV at 36 degrees C. Channels activated with a time constant of 13 +/- 1 ms at +20 mV, showed prominent inward rectification at depolarized potentials, were highly K(+) selective (Na(+)-to-K(+) permeability ratio = 0.007), and were potently inhibited by I(Kr) blockers. Astemizole, terfenadine, cisapride, and MK-499 inhibited cERG and human ERG (hERG) currents with IC(50) values of 1.3, 13, 19, and 15 nM and 1.2, 9, 14, and 21 nM, respectively, and competitively displaced [(35)S]MK-499 binding from cERG and hERG with IC(50) values of 0.4, 12, 35, and 0.6 nM and 0.8, 5, 47, and 0.7 nM, respectively. cERG channels had biophysical properties appropriate for canine action potential repolarization and were pharmacologically sensitive to agents known to prolong QT. A novel MK-499 binding assay provides a new tool to detect agents affecting ERG channels.