Effects of RP58866 on transmembrane K+ currents in mammalian ventricular myocytes.
OBJECTIVE
To determine effects of RP58866 on inward rectifier K+ current (IKl), transient outward K+ current (Ito) and delayed outward rectifier K+ current (IK) in isolated cardiac myocytes.


METHODS
In isolated ventricular myocytes of guinea pig and dog, the effect of RP58866 on IKl, Ito, and IK were observed by the whole cell voltage-clamp technique.


RESULTS
RP58866 decreased IKl in a concentration-dependent manner, with an IC50 of (3.4 +/- 0.8) micromol.L-1 (n = 6) at -100 mV in guinea pig ventricular cells. In dog ventricular myocytes, RP58866 inhibited Ito with IC50 of (2.3 +/- 0.5) micromol.L-1 at +40 mV. In guinea pig ventricular cells, RP58866 at 100 micromol.L-1 decreased IK: IKstep by (58 +/- 13)% at +40 mV, and IKtail by (86 +/- 17)%, respectively. RP58866 inhibited IKstep with an IC50 of (7.5 +/- 0.8) micromol.L-1, and IKtail with an IC50 of (3.5 +/- 0.9) micromol.L-1. The envelope of tail analysis suggested that both IKr and IKs were inhibited.


CONCLUSIONS
RP58866 inhibits IKl, Ito, and IK in cardiac myocytes with a similar potency, and is not a specific IKl inhibitor.
Department of Pharmacology, Harbin Medical University, Harbin 150086, China. Yangbf@ems.hrbmu.edu.cn
B F
BF
Yang
G R
GR
Li
C Q
CQ
Xu
S
S
Nattel
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D006168:Guinea Pigs; D006352:Heart Ventricles; D020128:Inhibitory Concentration 50; D008297:Male; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects*
D000889:Anti-Arrhythmia Agents; D002839:Chromans; D010880:Piperidines; D015221:Potassium Channels; C063899:terikalant