Block of human aorta Kir6.1 by the vascular K(ATP) channel inhibitor U37883A

Abstract

1. A human aorta cDNA library was screened at low stringency with a rat pancreatic Kir6.1 cDNA probe and a homologue of Kir6.1 (hKir6.1) was isolated and sequenced. 2. Metabolic poisoning of Xenopus laevis oocytes with sodium azide and application of the K+ channel opener drug diazoxide induced K+ channel currents in oocytes co-injected with cRNA for hKir6.1 and hamster sulphonylurea receptor (SUR1), but not in oocytes injected with water or cRNA for hKir6.1 or SUR1 alone. 3. K+ channel currents due to hKir6.1 + SUR1 or mouse Kir6.2 + SUR1 were strongly inhibited by 1 μM glibenclamide. K+-current carried by hKir6.1 a SUR1 was inhibited by the putative vascular-selective K(ATP) channel inhibitor U37883A (IC50 32 μM) whereas current carried by Kir6.2 + SUR1 or Shaker K+ channels was unaffected. 4. The data support the hypothesis that hKir6.1 is a component of the vascular K(ATP) channel, although the lower sensitivity of hKir6.1 + SUR1 to U37883A compared with native vascular tissues suggests the need for another factor or subunit. Furthermore, the data suggest that pharmacology of K(ATP) channels can be determined by the pore-forming subunit as well as the sulphonylurea receptor and point to a molecular basis for the pharmacological distinction between vascular and pancreatic/cardiac K(ATP) channels.