DOI:10.1590/S1807-59322010001200014 CLINICS 2010;65(12):1311-1314 CLINICAL SCIENCE Acute effect of phosphodiesterase type 5 inhibitor on serum oxidative status and prolidase activities in men with erectile dysfunction Murat Savas,I Ercan Yeni,I Ayhan Verit,I Mehmet Gulum,III Nurten Aksoy,II Halil Ciftci,II Hakim Celik,II Adem Altunkol,I Halil OncelI I Harran University, School of Medicine, Department of Urology, Sanliurfa, Turkey. II Harran University, School of Medicine, Department of Clinical Biochemistry, Sanliurfa, Turkey. III Sanliurfa Research Hospital, Department of Urology, Sanliurfa, Turkey. OBJECTIVES: To investigate the acute effect of phosphodiesterase type 5 (PDE5) inhibitor on erectile dysfunction by evaluating serum oxidative status and prolidase activity. METHODS: Serum samples of 36 patients with erectile dysfunction and 30 control cases were analyzed for total antioxidant status, total oxidant status, and prolidase activity, before and after the administration of tadalafil citrate. RESULTS: Before and after tadalafil citrate administration, serum total antioxidant status, total oxidant status, and prolidase were 1.1¡0.0 vs. 1.6¡0.0 mmol H2O2 Eq/L, 10.3¡1.1 vs. 6.9¡1.2 mmol H2O2 Eq/L, and 236.4¡19.5 vs. 228.2¡19.2 U/L, respectively (p,0.0001 for all). CONCLUSIONS: Evaluation of serum oxidative status and prolidase activity confirmed the beneficial acute effects of PDE5 inhibitor in patients with erectile dysfunction. KEYWORDS: Phosphodiesterase type 5 inhibitors; Tadalafil citrate; Total antioxidant status; Total oxidant status; Prolidase. Savas M, Yeni E, Verit A, Gulum M, Aksoy N, Ciftci H, Celik H, Altunkol A, Oncel H. Acute effect of phosphodiesterase type 5 inhibitor on serum oxidative status and prolidase activities in men with erectile dysfunction. Clinics. 2010;65(12):1311-1314. Received or publication on July 9, 2010; First review completed on August 1, 2010; Accepted for publication September 27, 2010 E-mail: mrtsvs@yahoo.com Tel.: +90 414 318 21 26 INTRODUCTION Although phosphodiesterase type 5 (PDE5) inhibitors were initially approved for the treatment of male erectile dysfunction (ED), their clinical spectrum has expanded owing to the enormous advances that have been made during the past decade. In preliminary studies, this progress in clinical practice was not restricted to human sexuality, either male or female, other than male ED, but extended to systemic disorders such as cardiovascular conditions and diabetes mellitus, owing to the beneficial effects of PDE5 inhibitors on endothelial functions, depression, pulmonary hypertension, pre-eclampsia, inflammation, chronic heart failure and renal insufficiency, hypertensive disorders, and even to cancer treatment, owing to induction of an apoptotic mechanism.1-5 It is well known that oxidative stress leads to impaired vasodilatation of the coronary, pulmonary, and peripheral Copyright 2010 CLINICS – This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non- commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 1311 vascular beds.6 There is limited information about the effect of PDE5 inhibitors on the serum oxidative mechanism, although its effect in restoring endothelial nitric oxide, which results in vasodilatation and inhibition of chemotaxis and platelet aggregation, is well known.7 In some studies sildenafil citrate has been shown to have protective effects against oxidative stress by inhibiting free radical formation and supporting antioxidant redox systems, and it is suggested that this reduced oxidative stress results in improvement of endothelial function.8,9 We have shown that serum prolidase activity is significantly associated with the presence and severity of vasculogenic ED, and elevated serum prolidase activity may be an independent predictor of ED.10 However, to our knowledge, the effect of the PD5 inhibitors on serum prolidase enzymes, which are closely related to serum oxidative status and endothelial functions, has not yet been documented. Prolidase is a cytosolic enzyme, necessary for specific splitting of imidodipeptides with proline or hydroxyproline at their C-terminals, and has a major role in collagen turnover and cell growth.10,11 The relationship between collagen and prolidase activity was observed during a study of fibrotic processes, where an increase in prolidase acti- vity was accompanied by an increase in tissue collagen