Paraoxonase-1 is only present in traceable amounts in seminal fluid and does not show any relationship with male subfertility

OBJECTIVE To characterise the immunohistochemical sites of paraoxonase (PON) 1, PON2 and PON3 in human testicular tissue, and to analyse PON1 levels in semen, aiming to investigate the role played by these enzymes in the pathophysiology of male subfertility. PATIENTS AND METHODS The present study was performed in 41 semen samples from normal donors and in 52 semen samples and ten testicle biopsies from patients who were being evaluated for causes of subfertility. RESULTS Immunohistochemical analyses showed high levels of PON1 and PON3 expression in testicular tissue. PON2 expression was also detected, albeit at weaker levels. Oxidative stress indicators in biopsies were low and localized in some specific areas of the seminiferous tubules. PON1 was detected in seminal fluid at very low levels but with no significant differences between patients and controls. Receiver-operating characteristic analysis showed a low diagnostic power of semen PON1 levels. CONCLUSIONS The present study shows high protein expression levels of PON1, PON2 and PON3 in testicular cells. The concentrations and activities of PON1 in semen are negligible and are probably the result of cellular catabolism, with no significant biological function in the testes.