Alterations in Arginase-NO-synthase System of Spermatozoa in Human Subjects with Different Fertility Potential

BACKGROUND: Infertility is an important worldwide problem which affects 10–15% of couples globally. Altered NO production has also been implicated in the pathogenesis of the male infertility. The present study was designed to evaluate the changes in the activity of NO-synthase (NOS) and arginase in spermatozoa of patients with infertility. METHODS: The total NOS, Ca(2+)-dependent constitutive (cNOS) and Ca(2+)-independent inducible (iNOS) activity and arginase activity were assessed in sperm cells of patients with different forms of pathospermia. RESULTS: We found a significant increase in iNOS activity, but significantly decreased cNOS and arginase activity in sperm cells of infertile men vs fertile, normozoospermic men (p<0.001). The arginase/NOS ratio significantly decreased compared to control group. The iNOS/cNOS ratio was drastically increased in patients with decreased fertility potential indicating predominance of iNOS. Men with leuko cytospermia were distinguished to have the most express iNOS activity. CONCLUSIONS: These observations provide evidence for a disturbed balance between the L-arginine metabolic pathways in sperm cells of infertile men. This imbalance includes the considerable activation of the inducible isoform of NO-synthase accompanied by significant inhibition of its constitutive isoform which indicates disturbances in NO production. In patients with decreased fertility potential the arginase/NOS was shifted towards predominance of iNOS-derived NO production.