Characterization of a novel Kv1.5 channel blocker in Xenopus oocytes, CHO cells, human and rat cardiomyocytes

The inhibitory effects of the novel Kv1.5 channel blocker, S9947 (2'-(benzyloxycarbonylaminomethyl)biphenyl-2-carboxylic acid 2-(2-pyridyl)ethylamide), on cloned human Kv1.5 (hKv1.5), expressed in both Xenopus oocytes and Chinese hamster ovary (CHO) cells, and on native cardiac uItrarapid delayed rectifier potassium currents (I-Kur) in rat (ventricle myocytes), and human (atrial myocytes) were investigated. The influence of S9947 on the action potential was examined in rat ventricular myocytes. Using the two-electrode voltage-clamp, technique in Xenopus oocytes and the patch-clamp technique (whole cell configuration) in CHO cells, hKv1.5 Was inhibited by S9947 with IC50 values of 0.65 muM and 0.42 muM, respectively. In addition, inhibition of human Kv4.3 (hKv4.3) and HERG by 10 muM S9947 was low (similar to 20%) and absent, respectively. Using the patch-clamp technique in the whole cell configuration, IK, currents in rat ventricular (r/(Kur)) cardiomyocytes and human atrial (h/(Kur)) cardiomyocytes were inhibited by S9947 with IC50 values of 0.96 muM and 0.07 muM, respectively. In contrast, rat cardiac inward rectifier current (r/(K1)) and rat (r/(to)) and human (h/(to)) cardiac transient outward currents were only inhibited by similar to 20% with 10 muM S9947. In rat cardiomyocytes, using the patch-clamp technique, action potential duration was increased by S9947 in a. concentration-dependent (0.3-10 muM) and rate-independent manner. The data show that S9947 suppresses both cloned (Kv1.5) and native (I-Kur) cardiac potassium, currents. Furthermore, S9947 prolongs rat action potential in a rate-independent manner.