Molecular Mechanisms of the Inhibitory Effects of Propofol and Thiamylal on Sarcolemmal Adenosine Triphosphate-sensitive Potassium Channels

Background: Both propofol and thiamylal inhibit adenosine triphosphate-sensitive potassium (KATP) channels. In the current study, the authors investigated the effects of these anesthetics on the activity of recombinant sarcolemmal KATP channels encoded by inwardly rectifying potassium channel (Kir6.1 or Kir6.2) genes and sulfonylurea receptor (SUR1, SUR2A, or SUR2B) genes.

Methods: The authors used inside-out patch clamp configurations to investigate the effects of propofol and thiamylal on the activity of recombinant KATP channels using COS-7 cells transfected with various types of KATP channel subunits.

Results: Propofol inhibited the activities of the SUR1/Kir6.2 (EC50 = 77 [mu]m), SUR2A/Kir6.2 (EC50 = 72 [mu]m), and SUR2B/Kir6.2 (EC50 = 71 [mu]m) channels but had no significant effects on the SUR2B/Kir6.1 channels. Propofol inhibited the truncated isoform of Kir6.2 (Kir6.2[DELTA]C36) channels (EC50 = 78 [mu]m) that can form functional KATP channels in the absence of SUR molecules. Furthermore, the authors identified two distinct mutations R31E (arginine residue at position 31 to glutamic acid) and K185Q (lysine residue at position 185 to glutamine) of the Kir6.2[DELTA]C36 channel that significantly reduce the inhibition of propofol. In contrast, thiamylal inhibited the SUR1/Kir6.2 (EC50 = 541 [mu]m), SUR2A/Kir6.2 (EC50 = 248 [mu]m), SUR2B/Kir6.2 (EC50 = 183 [mu]m), SUR2B/Kir6.1 (EC50 = 170 [mu]m), and Kir6.2[DELTA]C36 channels (EC50 = 719 [mu]m). None of the mutants significantly affects the sensitivity of thiamylal.