The objective of the present study was to characterize the role of adenosine in regulation of ATP-sensitive K+ channel (KATP channel) activity in isolated rabbit ventricular myocytes using the patch clamp technique. Internal adenosine had little effects on KaTr channel activity. In an outside-out patch with intrapipette GTP and ATP, external adenosine stimulated KATP channel activity. In an inside-out Patch with intrapipette adenosine, ATP reduced KATP channel activity, and GTP stimulated KATP channel activity. Adenosine receptor activation shifted the half-maximal inhibition Of KATP channel from 70 to 241 μm. These results Suggest that activation of adenosine receptors stimulates KATP channels in rabbit ventricular myocytes by reducing the apparent affinity of the channel for ATP. The effect may be important for activating KATP channels during early phase of myocardial ischemia.
