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Comparative Study
. 2005 Jan;2(1):53-7.
doi: 10.1111/j.1743-6109.2005.20105.x.

A nitric oxide-releasing PDE5 inhibitor relaxes human corpus cavernosum in the absence of endogenous nitric oxide

Jasjit S Kalsi  1 , David J Ralph, Phil Thomas, James Bellringer, Suks Minhas, Phil D Kell, Selim Cellek
Affiliations
Comparative Study

A nitric oxide-releasing PDE5 inhibitor relaxes human corpus cavernosum in the absence of endogenous nitric oxide

Jasjit S Kalsi et al. J Sex Med. 2005 Jan.

Abstract

Introduction: In conditions with severe deficiency of endogenous nitric oxide (NO), such as long-term diabetes and cavernosal nerve injury, phosphodiesterase type 5 (PDE5) inhibitors have reduced efficacy in the treatment of erectile dysfunction. NO-releasing PDE5 inhibitors could be an alternative therapeutic approach in such cases.

Aim: We therefore aimed to compare sildenafil and NO-releasing sildenafil (NCX-911) in relaxing human corpus cavernosum in the absence or presence of endogenous NO.

Methods: The two compounds were compared in reducing the phenylephrine-induced tone of human corpus cavernosum in the presence or absence of an inhibitor of NO synthase (L-NAME; 500 microM) or an inhibitor of soluble guanylate cyclase (ODQ, 10 microM).

Results: NCX-911 was as potent as sildenafil in control conditions (EC(50) = 733.1 +/- 94.4 nM and 800.7 +/- 155.8 nM, respectively). The potency of NCX-911 was not altered but that of sildenafil decreased significantly in the presence of L-NAME (EC(50) = 980.4 +/- 106.7 nM and 2446.7 +/- 256.8 nM, respectively; P < 0.001 for sildenafil vs. control). Both compounds below 1 microM failed to induce relaxation in the presence of ODQ (EC(50) = 6,578 +/- 1150 nM and 6,488 +/- 938 nM for NCX-911 and sildenafil, respectively).

Conclusion: These results show that the potency of NCX-911 was maintained unlike sildenafil in the absence of endogenous NO confirming the potential use of NO-releasing PDE5 inhibitors in NO-deficient conditions.

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