Pharmacological characterization of the relaxant effect induced by adrenomedullin in rat cavernosal smooth muscle

Autor(es)

L.N. Leite ^{[1, 2]} ; N.A. Gonzaga ^[1] ; D.P.C. Tirapelli ^[3] ; L.F. Tirapelli ^[3] ; C.R. Tirapelli ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Fac Med Ribeirao Preto, Programa Posgrad Farmacol, BR-14040902 Ribeirao Preto, SP - Brazil

^[2] Univ Sao Paulo, Escola Enfermagem Ribeirao Preto, Dept Enfermagem Psiquiatr & Ciencias Humanas, Farmacol Lab, BR-14040902 Ribeirao Preto, SP - Brazil

^[3] Univ Sao Paulo, Fac Med Ribeirao Preto, Dept Cirugia Anat, BR-14040902 Ribeirao Preto, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Brazilian Journal of Medical and Biological Research; v. 47, n. 10, p. 876-885, 2014-08-15.

Resumo

The aim of the present study was to determine the mechanisms underlying the relaxant effect of adrenomedullin (AM) in rat cavernosal smooth muscle (CSM) and the expression of AM system components in this tissue. Functional assays using standard muscle bath procedures were performed in CSM isolated from male Wistar rats. Protein and mRNA levels of pre-pro-AM, calcitonin receptor-like receptor (CRLR), and Subtypes 1, 2 and 3 of the receptor activity-modifying protein (RAMP) family were assessed by Western immunoblotting and quantitative real-time polymerase chain reaction, respectively. Nitrate and 6-keto-prostaglandin F1α (6-keto-PGF1α; a stable product of prostacyclin) levels were determined using commercially available kits. Protein and mRNA of AM, CRLR, and RAMP 1, -2, and -3 were detected in rat CSM. Immunohistochemical assays demonstrated that AM and CRLR were expressed in rat CSM. AM relaxed CSM strips in a concentration-dependent manner. AM22-52, a selective antagonist for AM receptors, reduced the relaxation induced by AM. Conversely, CGRP8-37, a selective antagonist for calcitonin gene-related peptide receptors, did not affect AM-induced relaxation. Preincubation of CSM strips with NG-nitro-L-arginine-methyl-ester (L-NAME, nitric oxide synthase inhibitor), 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, quanylyl cyclase inhibitor), Rp-8-Br-PET-cGMPS (cGMP-dependent protein kinase inhibitor), SC560 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethyl pyrazole, selective cyclooxygenase-1 inhibitor], and 4-aminopyridine (voltage-dependent K+ channel blocker) reduced AM-induced relaxation. On the other hand, 7-nitroindazole (selective neuronal nitric oxide synthase inhibitor), wortmannin (phosphatidylinositol 3-kinase inhibitor), H89 (protein kinase A inhibitor), SQ22536 [9-(tetrahydro-2-furanyl)-9H-purin-6-amine, adenylate cyclase inhibitor], glibenclamide (selective blocker of ATP-sensitive K+ channels), and apamin (Ca2+-activated channel blocker) did not affect AM-induced relaxation. AM increased nitrate levels and 6-keto-PGF1α in rat CSM. The major new contribution of this research is that it demonstrated expression of AM and its receptor in rat CSM. Moreover, we provided evidence that AM-induced relaxation in this tissue is mediated by AM receptors by a mechanism that involves the nitric oxide-cGMP pathway, a vasodilator prostanoid, and the opening of voltage-dependent K+ channels. (AU)

• Processo FAPESP: 06/60076-7 - Efeito do consumo crônico de etanol sobre o sistema adrenomedulina em aorta e leito mesentérico de ratos e avaliação do papel protetor desse peptídeo nas alterações vasculares induzidas pelo etanol
• Beneficiário: Carlos Renato Tirapelli
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores
• Processo FAPESP: 11/12911-2 - Consequências do consumo crônico de etanol sobre a reatividade e expressão dos componentes do sistema endotelinérgico em corpo cavernoso de rato
• Beneficiário: Carlos Renato Tirapelli
• Modalidade de apoio: Auxílio à Pesquisa - Regular