Important role of endothelium-derived hyperpolarizing factor in shear stress--induced endothelium-dependent relaxations in the rat mesenteric artery

J Cardiovasc Pharmacol. 1999 Sep;34(3):381-7. doi: 10.1097/00005344-199909000-00010.

Abstract

Shear stress is one of the most important stimulators for the release of endothelium-derived relaxing factors. Although shear stress-induced release of nitric oxide (NO) has been extensively investigated, it remains to be elucidated whether endothelium-derived hyperpolarizing factor (EDHF) contributes to the endothelium-dependent relaxations to shear stress. This study was designed to address this point in the isolated rat mesenteric artery. Large mesenteric arteries (400-500 microm) and resistance mesenteric arteries (150-250 microm) of the rat were precontracted with phenylephrine (at 80 mm Hg of perfusion pressure), and the changes in vessel diameter in response to variable flow (0-300 microl/min) were continuously examined. The relative contributions of vasodilator prostaglandins, NO, and EDHF were analyzed by the inhibitory effects of indomethacin (10(-5) M), N(G)-nitro-L-arginine (L-NNA, 10(-4) M), and KCl (40 mM), respectively. The shear stress-induced relaxations were totally endothelium dependent in both-sized blood vessels, and the contribution of NO was more prominent in large arteries than in resistance arteries, whereas that of EDHF was noted in both-sized blood vessels. Tetrabutylammonium (a nonselective inhibitor of K channels) almost abolished, whereas the combination of charybdotoxin (an inhibitor of both large- and intermediate-conductance Ca2+ -activated K channels) and apamin (an inhibitor of small-conductance Ca2+ -activated K channels) significantly inhibited the EDHF-mediated component of the shear stress-induced relaxations. These results indicate that EDHF plays an important role in shear stress-induced endothelium-dependent relaxations, where K channels, especially calcium-activated K channels, appear to be involved.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Factors / physiology*
  • Endothelium, Vascular / drug effects
  • Endothelium, Vascular / physiology*
  • Hemorheology
  • In Vitro Techniques
  • Male
  • Mesenteric Arteries / drug effects
  • Mesenteric Arteries / physiology*
  • Nitric Oxide / pharmacology
  • Prostaglandins / pharmacology
  • Rats
  • Rats, Inbred WKY
  • Vasodilation* / drug effects
  • Vasodilator Agents / pharmacology

Substances

  • Biological Factors
  • Prostaglandins
  • Vasodilator Agents
  • endothelium-dependent hyperpolarization factor
  • Nitric Oxide