Potentiation of EDHF-mediated relaxation by chloride channel blockers

Acta Pharmacol Sin. 2010 Oct;31(10):1303-11. doi: 10.1038/aps.2010.157. Epub 2010 Sep 13.


Aim: To investigate the involvement of Cl⁻ channels in endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation in rat mesenteric arteries.

Methods: Cl⁻ channel and K(ir) channel activities were studied using whole-cell patch clamping in rat mesenteric arterial smooth muscle cells. Isometric tension of arterial rings was measured in organ chambers.

Results: The volume-activated Cl⁻ current in rat mesenteric arterial smooth muscle cells was abolished by Cl⁻ channel blockers NPPB or DIDS. The EDHF-mediated vasorelaxation was potentiated by NPPB and DIDS. The EDHF response was diminished by a combination of apamin and charybdotoxin, which agreed with the hypothesis that EDHF response involves the release of K(+) via the Ca²(+)-activated K(+) channels in endothelial cells. The elevation of K(+) concentration in bathing solution from 1.2 mmol/L to 11.2 mmol/L induced an arterial relaxation, which was abolished by the combination of BaCl₂ and ouabain. It is consistent to the hypothesis that K(+) activates K(+)/Na(+)-ATPase and inward rectifier K(+) (K(ir)) channels, leading to the hyperpolarization and relaxation of vascular smooth muscle. The K(+)-induced relaxation was augmented by NPPB, DIDS, or withdrawal of Cl⁻ from the bathing solution, which could be reversed by BaCl₂, but not ouabain. The potentiating effect of Cl⁻ channel blockers on K(+)-induced relaxation was probably due to the interaction between Cl⁻ channels and K(ir) channels. Moreover, the K(+)-induced relaxation was potentiated when the arteries were incubated in hyperosmotic solution, which is known to inhibit volume-activated Cl⁻ channels.

Conclusion: The inhibition of Cl⁻ channels, particularly the volume-activated Cl⁻ channels, may potentiate the EDHF-induced vasorelaxation through the K(ir) channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / pharmacology*
  • Animals
  • Apamin / pharmacology
  • Charybdotoxin / pharmacology
  • Chloride Channels / antagonists & inhibitors*
  • Endothelium-Dependent Relaxing Factors / physiology*
  • In Vitro Techniques
  • Male
  • Membrane Potentials / drug effects
  • Mesenteric Arteries / drug effects*
  • Mesenteric Arteries / physiology
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / physiology
  • Nitrobenzoates / pharmacology*
  • Osmolar Concentration
  • Potassium Channels, Inwardly Rectifying / antagonists & inhibitors
  • Rats
  • Rats, Sprague-Dawley
  • Vasodilation / drug effects*


  • Chloride Channels
  • Endothelium-Dependent Relaxing Factors
  • Nitrobenzoates
  • Potassium Channels, Inwardly Rectifying
  • Charybdotoxin
  • Apamin
  • 5-nitro-2-(3-phenylpropylamino)benzoic acid
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid