NITRIC-OXIDE SYNTHASE AND XANTHINE-OXIDASE ACTIVITIES IN THE SPERMATIC VEIN OF PATIENTS WITH VARICOCELE - A POTENTIAL ROLE FOR NITRIC-OXIDEAND PEROXYNITRITE IN SPERM DYSFUNCTION

Purpose: The oxidative and reductive stresses within the varicocele ve ins were estimated. Nitric oxide synthase and xanthine oxidase activit ies, as well as nitric oxide, S-nitrosothiols and superoxide release w ithin the spermatic vein in patients with varicocele, and the role of the noxious oxidant peroxynitrite formed from nitric oxide and superox ide in sperm dysfunction were determined. Materials and Methods: Whole blood samples were drawn from a peripheral vein and a dilated varicoc ele vein before ligation. Nitric oxide synthase, xanthine oxidase, nit ric oxide and peroxynitrite were measured by novel spectro-fluorophoto metric methods. S-nitrosothiols were estimated by a luminol-chemilumin escence method. Serum and red blood cell antioxidant capacity was dete rmined by a chemiluminescence reaction. Results: Serum nitric oxide sy nthase and xanthine oxidase activities, as well as nitric oxide, perox ynitrite and S-nitrosothiol levels were greater in the spermatic vein compared to the peripheral vein. Serum antioxidant capacity was greate r in varicocele veins compared to peripheral veins. In contrast, the a ntioxidant capacity of red blood cells was less in the varicocele vein s, which was consistent with an increased rate of peroxynitrite produc tion. Conclusions: Our data suggest a high oxidative stress due to the release of nitric oxide synthase and xanthine oxidase within the dila ted spermatic vein. This reaction resulted in dramatic formation of ni tric oxide, peroxynitrite and S-nitrosothiols, which are biologically active. Formation of peroxynitrite from the reaction of nitric oxide w ith superoxide could be a causative factor for impaired sperm function in patients with varicocele.