Pharmacology of ATP-sensitive K+ currents in smooth muscle cells from rabbit mesenteric artery.
The inference that ATP-sensitive K+ (KATP) channels are involved in arterial responses to the synthetic K+ channel openers, hypoxia, adenosine, and calcitonin gene-related peptide, has relied on the sensitivity of these responses to the sulfonylureas glibenclamide and tolbutamide and to tetraethylammonium (TEA+). The inhibition of KATP currents by glibenclamide, tolbutamide, and TEA+ was investigated in single smooth muscle cells from rabbit mesenteric artery by use of the whole cell patch-clamp technique. The synthetic K+ channel openers pinacidil (half-activation 0.6 microM), cromakalim (half-activation 1.9 microM), and diazoxide (half-activation 37.1 microM) activated K(+)-selective currents that were blocked by glibenclamide. Elevation of pipette (intracellular) ATP concentration decreased K+ currents induced by pinacidil. Half-inhibition of KATP currents by glibenclamide and tolbutamide occurred at 101 nM and 351 microM, respectively. KATP currents were also inhibited by external TEA+, with half-inhibition at 6.2 mM. The results indicate that glibenclamide is an effective inhibitor of KATP channels in arterial smooth muscle and that tolbutamide and TEA+ are much less effective. Furthermore, these results support numerous functional studies that have demonstrated that the vasorelaxations to K+ channel openers are inhibited by < 10 microM glibenclamide but not by < 1 mM TEA+.
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004553:Electric Conductivity; D005905:Glyburide / Q000494:pharmacology; D008638:Mesenteric Arteries / Q000166:cytology / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D013453:Sulfonylurea Compounds / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013453:Sulfonylurea Compounds; D013757:Tetraethylammonium Compounds; D014665:Vasodilator Agents; D019789:Tetraethylammonium; D000255:Adenosine Triphosphate; D005905:Glyburide