Activation of endothelial nitric oxide synthase by proanthocyanidin-rich fraction from Croton celtidifolius (Euphorbiaceae): involvement of extracellular calcium influx in rat thoracic aorta

J Pharmacol Sci. 2008 Jun;107(2):181-9. doi: 10.1254/jphs.fp0072385.

Abstract

The present study investigates the mechanisms related to the endogenous nitric oxide synthase (eNOS) activation in the relaxant effects of a proanthocyanidin-rich fraction (PRF), obtained from Croton celtidifolius Baill barks, in rat thoracic aorta rings with endothelium. In vessels pre-contracted with phenylephrine (Phe), PRF (0.1 - 100 microg/mL) induced a concentration-dependent relaxation. This effect was significantly reduced by endothelium denudation, by N(omega)-nitro-L-arginine, and by 1H[1,2,3]oxadiazolo[4,3-alpha]quinoxalin. However, the vasorelaxant effect was not altered by indomethacin, atropine, tetraethylammonium, and charybdotoxin plus apamin. In thoracic aorta rings pre-contracted with phorbol-12,13-dibuyrate, PRF also induced a concentration-dependent relaxation. The PRF-induced relaxation disappeared in the absence of extracellular calcium in the medium and decreased significantly in the presence of lanthanum. A sulfhydryl alkylating agent, N-ethylmaleimide, and a phospholipase C (PLC) blocker, neomycin, significantly decreased PRF-induced vasorelaxation. In vessels pre-contracted with Phe, the PRF-induced vasorelaxant effect was not altered by quinacrine and ONO-RS-082, genistein and thyrphostin A-23, GF109203, and pertussis toxin and cholera toxin. The results suggest that the PRF-induced vasorelaxant effect is endothelium-dependent and involves the NO/cGMP pathway. We hypothesize that the activation of eNOS is due to an increase of intracellular calcium derived from PLC activation and an N-ethylmaleimide sensitive pathway.

MeSH terms

  • Animals
  • Aorta, Thoracic / metabolism*
  • Calcium / metabolism*
  • Croton / chemistry*
  • Dose-Response Relationship, Drug
  • Enzyme Activation
  • Ethylmaleimide / pharmacology
  • In Vitro Techniques
  • Male
  • Nitric Oxide / physiology
  • Nitric Oxide Synthase Type III / metabolism*
  • Nitroarginine / pharmacology
  • Proanthocyanidins / pharmacology*
  • Rats
  • Rats, Wistar
  • Type C Phospholipases / physiology

Substances

  • Proanthocyanidins
  • proanthocyanidin
  • Nitroarginine
  • Nitric Oxide
  • Nitric Oxide Synthase Type III
  • Type C Phospholipases
  • Ethylmaleimide
  • Calcium