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Pharmacology of ATP-sensitive K+ currents in smooth muscle cells from rabbit mesenteric artery.
Quayle J, Bonev A, Brayden J, Nelson MT
American Journal of Physiology-Cell Physiology. 1995;269( 5 Pt 1):C1112-8.
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Abstract
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+.
Keyword(s)
Animals; Cells, Cultured; Electric Conductivity; Potassium Channel Blockers; Rabbits; Tetraethylammonium; cytology: Mesenteric Arteries; cytology: Muscle, Smooth, Vascular; drug effects: Potassium Channels; pharmacology: Adenosine Triphosphate; pharmacology: Glyburide; pharmacology: Sulfonylurea Compounds; pharmacology: Tetraethylammonium Compounds; pharmacology: Vasodilator Agents