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Vasorelaxation, Induced by Dictyota pulchella (Dictyotaceae), a Brown Alga, Is Mediated via Inhibition of Calcium Influx in Rats
Biotechnology Center, Federal University of Paraiba, João Pessoa, PB 58.051-900, Brazil
* Author to whom correspondence should be addressed.
Received: 23 August 2011; in revised form: 13 October 2011 / Accepted: 17 October 2011 / Published: 24 October 2011
Abstract: This study aimed to investigate the cardiovascular effects elicited by Dictyota pulchella, a brown alga, using in vivo and in vitro approaches. In normotensive conscious rats, CH2Cl2/MeOH Extract (CME, 5, 10, 20 and 40 mg/kg) from Dictyota pulchella produced dose-dependent hypotension (−4 ± 1; −8 ± 2; −53 ± 8 and −63 ± 3 mmHg) and bradycardia (−8 ± 6; −17 ± 11; −257 ± 36 and −285 ± 27 b.p.m.). In addition, CME and Hexane/EtOAc Phase (HEP) (0.01–300 µg/mL) from Dictyota pulchella induced a concentration-dependent relaxation in phenylephrine (Phe, 1 µM)-pre-contracted mesenteric artery rings. The vasorelaxant effect was not modified by the removal of the vascular endothelium or pre-incubation with KCl (20 mM), tetraethylammonium (TEA, 3 mM) or tromboxane A2 agonist U-46619 (100 nM). Furthermore, CME and HEP reversed CaCl2-induced vascular contractions. These results suggest that both CME and HEP act on the voltage-operated calcium channel in order to produce vasorelaxation. In addition, CME induced vasodilatation after the vessels have been pre-contracted with L-type Ca2+ channel agonist (Bay K 8644, 200 nM). Taken together, our data show that CME induces hypotension and bradycardia in vivo and that both CME and HEP induce endothelium-independent vasodilatation in vitro that seems to involve the inhibition of the Ca2+ influx through blockade of voltage-operated calcium channels.
Keywords: calcium; hypotension; mesenteric artery; vasodilatation
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Queiroz, T.M.; Machado, N.T.; Furtado, F.F.; Oliveira-Filho, A.A.; Alustau, M.C.; Figueiredo, C.S.; Miranda, G.E.C.; Barbosa-Filho, J.M.; Braga, V.A.; Medeiros, I.A. Vasorelaxation, Induced by Dictyota pulchella (Dictyotaceae), a Brown Alga, Is Mediated via Inhibition of Calcium Influx in Rats. Mar. Drugs 2011, 9, 2075-2088.
Queiroz TM, Machado NT, Furtado FF, Oliveira-Filho AA, Alustau MC, Figueiredo CS, Miranda GEC, Barbosa-Filho JM, Braga VA, Medeiros IA. Vasorelaxation, Induced by Dictyota pulchella (Dictyotaceae), a Brown Alga, Is Mediated via Inhibition of Calcium Influx in Rats. Marine Drugs. 2011; 9(10):2075-2088.
Queiroz, Thyago M.; Machado, Natália T.; Furtado, Fabíola F.; Oliveira-Filho, Abrahão A.; Alustau, Maria C.; Figueiredo, Camila S.; Miranda, George E. C.; Barbosa-Filho, José M.; Braga, Valdir A.; Medeiros, Isac A. 2011. "Vasorelaxation, Induced by Dictyota pulchella (Dictyotaceae), a Brown Alga, Is Mediated via Inhibition of Calcium Influx in Rats." Mar. Drugs 9, no. 10: 2075-2088.