Direct inhibition by taurine of the ATP-sensitive k+ channel in guinea pig ventricular cardiomyocytes.
1. 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.
Satoh
H
H
Department of Pharmacology, Nara Medical University, Japan.
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D005905:Glyburide / Q000494:pharmacology; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects; D007004:Hypoglycemic Agents / Q000494:pharmacology; D066298:In Vitro Techniques; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D013654:Taurine / Q000494:pharmacology*
D007004:Hypoglycemic Agents; D015221:Potassium Channels; D013654:Taurine; D000255:Adenosine Triphosphate; D005905:Glyburide