JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
Issue Date:
1991
Abstract(summary):
UK-68,798 increased the duration and effective refractory period of cardiac action potentials recorded in vitro from canine ventricular muscle and Purkinje fibers in a concentration dependent manner from 5 nM to 1-mu-M. The resting membrane potential, amplitude and maximum upstroke velocity of action potentials were unaffected by UK-68,798, indicating the selective class III antiarrhythmic properties of this agent. UK-68,798 (5 nM-1-mu-M) increased the effective refractory period of isolated guinea pig papillary muscles at stimulation frequencies of 1 Hz and 5 Hz without influencing the conduction velocity, further confirming that UK-68,798 is devoid of class 1 antiarrhythmic activity including block of the sodium channel. Studies using single voltage clamped guinea pig ventricular myocytes indicated that UK-68,798 at concentrations of 50 nM and 2-mu-M blocks a time-dependent K+ current, with no appreciable effects on the time-independent K+ current or the inward calcium current. UK-68,798 is therefore a highly selective K+ channel blocking agent with class III antiarrhythmic properties, a profile that holds considerable promise for the therapy of life-threatening cardiac arrhythmias.