RESUMO
<p><b>AIM</b>To evaluate the genetic instability of 11 fertile and 25 infertile men.</p><p><b>METHODS</b>The methodology of sister chromatid exchanges (SCEs) was applied to cultures of peripheral blood lymphocytes, and the levels of SCEss were analyzed as a quantitative index of genotoxicity, along with the values of the mitotic index (MI) and the proliferation rate index (PRI) as qualitative indices of cytotoxicity and cytostaticity, respectively. The genotoxic and antineoplastic agent, mitomycin C (MMC), and caffeine (CAF)--both well-known inhibitors of DNA repair mechanism--were used in an attempt to induce chromosomal instability in infertile men, so as to more easily detect the probable underlying damage on DNA.</p><p><b>RESULTS</b>Our experiments illustrated that infertile men, compared with fertile ones, demonstrated a statistically significant DNA instability in peripheral blood lymphocytes after being exposed simultaneously to MMC and CAF.</p><p><b>CONCLUSION</b>The current study showed vividly that there was genetic instability in infertile men which probably contributes to the development of an impaired reproductive capacity.</p>