Effects of taurine on the ATP-sensitive K+ channel in isolated guinea pig ventricular cardiomyocytes were examined using an inside-out patch voltage-clamp mode. All experiments were performed at 36 degrees C. 2. The ATP-sensitive K+ channel was activated outwardly. ATP-free and 140 mM K+ solution in the bath and 140 mM K+ in the pipette solution were used. The amplitude was 2.2 +/- 0.3 pA (n = 9) at + 50 mV. The channel conductance was 31 +/- 3 pS (n = 9). Glibenclamide (1 microM) blocked the channel opening. 3. Taurine decreased the open probability (as a mean patch current for 30 sec) of the channel by 21.5 +/- 2.4% (n = 8, P < 0.01) at 10 mM, and almost blocked it (n = 8, P < 0.001) at 20 mM. 4. Taurine did not affect the channel conductance; these responses were reversible. 5. These results suggest that taurine directly modulates the open probability of the ATP-sensitive K+ channel, resulting in regulation of the cell functions.
