Activation of ATP-sensitive outward K + current by nicorandil (2-nicotinamidoethyl nitrate) in isolated ventricular myocytes

The vasodilatory agent, nicorandil (2-nicotinamidoethyl nitrate) activates an outward K current in cardiac and vascular smooth muscle. This current was studied with the patch clamp technique using isolated guinea pig and rabbit ventricular myocytes. Nicor-andil (1 0 and 1 0 M) shortened the action potential duration without any significant change in the resting membrane potential. Under voltage damp, nicorandil increased the time-independent outward current at potentials positive to-80 mV, and decreased the inward current at potentials negative to-90 mV. The drug did not affect Ca current activated upon depolarization from the holding potential of-30 mV, or did it influence delayed outward K current on repolanzation. In rabbit myocytes, nicor-andil did not increase the Ca-sensitive and-insensitive tran-sient outward K currents. When the ATP concentration of th