title: Mechanisms underlying the vasorelaxant action of the pimarane ent-8(14),15-pimaradien-3beta-ol in the isolated rat aorta.
abstract: Pimarane-type diterpenes were described to exert antispasmodic and relaxant activities. Based on this observation we hypothesized that the diterpene ent-8(14),15-pimaradien-3beta-ol (PA-3beta-ol) induced vascular relaxation. With this purpose, the present work investigates the mechanisms involved in the vasorelaxant effect of the pimarane-type diterpene PA-3beta-ol. Vascular reactivity experiments, using standard muscle bath procedures, were performed in isolated aortic rings from male Wistar rats. Cytosolic calcium concentration ([Ca(2+)]c) was measured by confocal microscopy using the fluorescent probe Fluo-3AM. PA-3beta-ol (10, 50 and 100 micromol/l) inhibited phenylephrine and KCl-induced contraction in either endothelium-intact or denuded rat aortic rings. PA-3beta-ol also reduced CaCl(2)-induced contraction in Ca(2+)-free solution containing KCl (30 mmol/l) or phenylephrine (0.1 micromol/l). PA-3beta-ol (1-300 micromol/l) concentration dependently relaxed phenylephrine-pre-contracted rings with intact or denuded endothelium. The diterpene also relaxed KCl-pre-contracted rings with intact or denuded endothelium. Moreover, Ca(2+) mobilization study showed that PA-3beta-ol (100 micromol/l) and verapamil (1 micromol/l) inhibited the increase in Ca(2+)-concentration in smooth muscle and endothelial cells induced by phenylephrine (10 micromol/l) or KCl (60 mmol/l). Pre-incubation of intact or denuded aortic rings with N(G)-nitro-l-arginine methyl ester (L-NAME, 100 micromol/l) and 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 1 micromol/l) produced a rightward displacement of the PA-3beta-ol concentration-response curves. On the other hand, 7-nitroindazole (100 micromol/l), 1400 W (1 micromol/l), indomethacin (10 micromol/l) and tetraethylammonium (1 mmol/l) did not affect PA-3beta-ol-induced relaxation. Collectively, our results provide evidence that the effects elicited by PA-3beta-ol involve extracellular Ca(2+) influx blockade. Its effects are also partly mediated by the activation of NO-cGMP pathway.
authors.affiliation: Department of Psychiatric Nursing and Human Sciences, College of Nursing of Ribeirão Preto, University de São Paulo (USP), Ribeirão Preto, SP, Brazil. vilelahipolito@yahoo.com.br
authors.forename: Ulisses V
authors.initials: UV
authors.lastname: Hipólito
authors.forename: Gerson J
authors.initials: GJ
authors.lastname: Rodrigues
authors.forename: Claure N
authors.initials: CN
authors.lastname: Lunardi
authors.forename: Daniella
authors.initials: D
authors.lastname: Bonaventura
authors.forename: Sergio R
authors.initials: SR
authors.lastname: Ambrosio
authors.forename: Ana M
authors.initials: AM
authors.lastname: de Oliveira
authors.forename: Lusiane M
authors.initials: LM
authors.lastname: Bendhack
authors.forename: Fernando B
authors.initials: FB
authors.lastname: da Costa
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Tirapelli
mesh_terms: D045784:Abietanes / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002122:Calcium Chloride / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D066298:In Vitro Techniques; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D009119:Muscle Contraction / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014664:Vasodilation / Q000187:drug effects*
chemical_list: C544314:8(14),15-pimaradien-3-bol; D045784:Abietanes; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D010656:Phenylephrine; D009569:Nitric Oxide; D011189:Potassium Chloride; D006152:Cyclic GMP; D002122:Calcium Chloride; D002118:Calcium