Activation of endothelial nitric oxide synthase by proanthocyanidin-rich fraction from Croton celtidifolius (Euphorbiaceae): involvement of extracellular calcium influx in rat thoracic aorta.
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.
DalBó
Silvia
S
Departamento de Farmacologia, Centro de Ciências Biológicas (CCB), Universidade Federal de Santa Catarina (UFSC), Florianópolis, SC, Brazil.
Goulart
Suelen
S
Horst
Heros
H
Pizzolatti
Moacir Geraldo
MG
Ribeiro-do-Valle
Rosa Maria
RM
D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D029802:Croton / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005033:Ethylmaleimide / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009569:Nitric Oxide / Q000502:physiology; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D019335:Nitroarginine / Q000494:pharmacology; D044945:Proanthocyanidins / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D010738:Type C Phospholipases / Q000502:physiology
D044945:Proanthocyanidins; C013221:proanthocyanidin; D019335:Nitroarginine; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D010738:Type C Phospholipases; D005033:Ethylmaleimide; D002118:Calcium