Leite LN, Gonzaga NA, Tirapelli DPC, Tirapelli LF, Tirapelli CR. Pharmacological characterization of the relaxant effect induced by adrenomedullin in rat cavernosal smooth muscle.
Braz J Med Biol Res 2014;
47:876-85. [PMID:
25140812 PMCID:
PMC4181223 DOI:
10.1590/1414-431x20143911]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 05/09/2014] [Indexed: 11/22/2022] Open
Abstract
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.
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