The comparison of the relaxant effects of two methoxylated flavones in rat aortic rings

Vascul Pharmacol. 2005 Oct;43(4):220-6. doi: 10.1016/j.vph.2005.07.002. Epub 2005 Oct 5.

Abstract

The vascular effect of salvigenin (6-hydroxyapigenin 6,7,4' -trimethyl ether), a natural flavone, was investigated in comparison with another flavone, 6-hydroxyluteolin 6,7,3',4' -tetramethyl ether in rat aortic rings. Cumulative addition of their increasing concentrations (10(-9)-10(-4)M) produced graded relaxations on rings precontracted with noradrenaline (10(-6) M) and KCl (40 mM). The maximal relaxations induced by flavones were similar, however, based on their pEC50 values salvigenin displayed a higher potency than 6-hydroxyluteolin 6,7,3',4'-tetramethyl ether. Endothelium removal markedly reduced the relaxations to salvigenin while the responses to 6-hydroxyluteolin 6,7,3',4'-tetramethyl ether were partially affected. In addition, a significant decrease was observed in maximal responsiveness and sensitivity to flavones in the presence of L-NOARG, a NO synthase inhibitor. The cyclooxygenase inhibitor indomethacin significantly inhibited the relaxations to salvigenin, but not altered the responses to 6-hydroxyluteolin 6,7,3',4'-tetramethyl ether. Our results provide evidence that salvigenin is an effective flavone in causing vasorelaxation which appears to be mediated by endothelium derived NO and prostacyclin. Whereas, the other flavone, 6-hydroxyluteolin 6,7,3',4'-tetramethyl ether induced relaxant responses are partially endothelium, presumably NO mediated.

Publication types

  • Comparative Study

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Aorta, Thoracic / drug effects*
  • Endothelium, Vascular / physiology
  • Enzyme Inhibitors / pharmacology
  • Flavones / pharmacology*
  • In Vitro Techniques
  • Luteolin / pharmacology
  • Male
  • Muscle Relaxation / drug effects
  • Muscle, Smooth, Vascular / drug effects*
  • Nitric Oxide Synthase Type III / antagonists & inhibitors
  • Nitroarginine / pharmacology
  • Nitroprusside / pharmacology
  • Norepinephrine / pharmacology
  • Potassium / pharmacology
  • Rats
  • Rats, Wistar
  • Vasodilator Agents / pharmacology

Substances

  • Enzyme Inhibitors
  • Flavones
  • Vasodilator Agents
  • Nitroprusside
  • 6-hydroxyluteolin
  • salvigenin
  • Nitroarginine
  • Nitric Oxide Synthase Type III
  • Luteolin
  • Acetylcholine
  • Potassium
  • Norepinephrine