Comparative Relaxing Effects of Sildenafil, Vardenafil, and Tadalafil in Human Corpus Cavernosum: Contribution of Endogenous Nitric Oxide Release - 07/08/11
Résumé |
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 μmol/L).
Results |
All PDE-5 inhibitors tested (0.001-10 μmol/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 μmol/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 μmol/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 μmol/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.
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Vol 74 - N° 1
P. 216-221 - juillet 2009 Retour au numéroBienvenue sur EM-consulte, la référence des professionnels de santé.
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