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|Type:||Artigo de periódico|
|Title:||Comparative Relaxing Effects of Sildenafil, Vardenafil, and Tadalafil in Human Corpus Cavernosum: Contribution of Endogenous Nitric Oxide Release|
De Nucci, G
|Abstract:||OBJECTIVES To compare the direct relaxant activity of sildenafil, vardenafil, and tadalafil in the human corpus cavernosum (HCC) and to investigate their modulatory effects on nitric oxide (NO)-mediated responses. Phosphodiesterase (PDE)-5 inhibitors cause cavernosal smooth muscle relaxation and penile erection. METHODS HCC strips were mounted in 10-mL organ baths containing Krebs solution and connected to force-displacement transducers. The changes in isometric force were recorded using the Powerlab 400 data acquisition system. Corporeal smooth muscle was precontracted submaximally with phenylephrine (10 mu mol/L). RESULTS All PDE-5 inhibitors tested (0.001-10 mu mol/L) relaxed phenylephrine-precontracted HCC with similar values of potency in a concentration-dependent manner. However, the maximal relaxations induced by tadalafil (83% +/- 4%) were significantly lower compared with sildenafil (107% +/- 5%) and vardenafil (111% +/- 3%). The NO synthesis inhibitor N-nitro-L-arginine methyl ester (100 mu mol/L) caused significant rightward shifts in the concentration-response curves for sildenafil (4.0-fold), vardenafil (4.6-fold), and tadalafil (3.2-fold) in HCC tissue. The guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,a]quinoxalin-1-one (10 mu mol/L) also produced similar rightward shifts for these PDE-5 inhibitors. The cavernosal relaxations evoked by either acetylcholine or the NO donor glyceryl trinitrate were markedly potentiated by sildenafil, vardenafil, and tadalafil (0.1 mu mol/L each). All PDE-5 inhibitors significantly increased the duration of electrical field stimulation-induced relaxations (8 Hz). CONCLUSIONS Our findings have shown that sildenafil, vardenafil, and tadalafil relax HCC tissues in a concentration-dependent manner, but the maximal relaxation obtained with tadalafil was significantly lower than that obtained with sildenafil and vardenafil. Moreover, the PDE-5 inhibitors interacted with endogenous and exogenous NO, amplifying its HCC relaxation. UROLOGY 74: 216-221, 2009. (c) 2009 Elsevier Inc.|
|Editor:||Elsevier Science Inc|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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