Effect of pH on the ATP-sensitive K<SUP>&#8290;</SUP> Channel in Aortic Smooth Muscle Cells from Rats

Effect of pH on the ATP-sensitive K<SUP>&#8290;</SUP> Channel in Aortic Smooth Muscle Cells from Rats

<P> The effects of pH on K<SUP>&#8290;</SUP> currents were investigated in single smooth muscle cells isolated from the thoracic aorta of Wistar-Kyoto rats. Whole-cell K<SUP>&#8290;</SUP> currents were recorded in the conventional configuration of the voltage-clamp technique. Pinacidil (10uM) activated the whole-cell current and the pinacidil-activated current was completely inhibited by glibenclamide (10uM) , an inhibitor of ATP-sensitive K<SUP>&#8290;</SUP> channel (K<SUB>ATP</SUB> channel). Pinacidil-activated current was reversed at near the K<SUP>&#8290;</SUP> equilibrium potential. This current was time- and voltage-independent and reduced by elevating intracellular ATP. Pinacidil-activated current was reduced by lowering the external pH. However, alteration of internal pH has controversial effects on pinacidil-activated current. When the single cell was dialyzed with 0.1 mM ATP, alteration of internal pH had no effect on pinacidil-activated K<SUP>&#8290;</SUP> current. In the contrast, when the single cell was dialyzed with 3 mM ATP, pinacidil-activated current was increased by lowering internal pH. Our results suggest that K<SUP>&#8290;</SUP> channel activated by pinacidil may be K<SUB>ATP</SUB> channel and internal H<SUP>&#8290;</SUP> may reduce the inhibitory effect of ATP on K<SUB>ATP</SUB> channel.