Related Experiment Videos
Block of human aorta Kir6.1 by the vascular KATP channel inhibitor U37883A
S Surah-Narwal1, S Z Xu, D McHugh
1School of Biomedical Sciences, Worsley Building, University of Leeds, Leeds, LS2 9JT, UK.
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 microM glibenclamide. K+-current carried by hKir6.1+SUR1 was inhibited by the putative vascular-selective KATP channel inhibitor U37883A (IC50 32 microM) 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 KATP 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 KATP 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 KATP channels.
Insights
Human Kir6.1 (hKir6.1) is identified as a component of vascular ATP-sensitive potassium (KATP) channels. Its function with SUR1 suggests a molecular basis for distinguishing vascular KATP channel pharmacology.
Area of Science:
- Molecular biology
- Cardiovascular research
- Ion channel physiology
Background:
- ATP-sensitive potassium (KATP) channels are crucial in regulating vascular tone.
- The specific subunits forming vascular KATP channels and their pharmacological properties remain incompletely understood.
Purpose of the Study:
- To isolate and characterize a human homologue of the rat pancreatic Kir6.1 gene.
- To investigate the functional role and pharmacological properties of the human Kir6.1 (hKir6.1) subunit in KATP channels.
Main Methods:
- Screening a human aorta cDNA library to isolate hKir6.1.
- Expressing hKir6.1 and SUR1 in Xenopus oocytes to study K+ channel activity.
- Assessing the effects of KATP channel modulators (diazoxide, glibenclamide, U37883A) on expressed channels.
Main Results:
- hKir6.1 was isolated and sequenced.
- Co-expression of hKir6.1 and SUR1 in oocytes generated functional K+ channels activated by diazoxide and inhibited by glibenclamide.
- hKir6.1+SUR1 channels showed sensitivity to the vascular-selective inhibitor U37883A, albeit with lower potency than native vascular tissues.
Conclusions:
- hKir6.1 is a likely component of vascular KATP channels.
- The pore-forming subunit (Kir6.1) influences KATP channel pharmacology, contributing to distinctions between vascular and other KATP channel types.
- Additional factors may be involved in conferring the full pharmacological profile of native vascular KATP channels.