RESUMEN
<p><b>OBJECTIVE</b>To investigate the in vivo effects of nanosized titanium dioxide (TiO2) on the main organs, particularly the reproductive system, of male mice.</p><p><b>METHODS</b>Forty-five male ICR mice aged 6 weeks were equally and randomly divided into 2 experimental groups and a control group, intraperitoneally injected with 200 and 500 mg/kg nanosized TiO2 and equal volume of saline, respectively, every other day for 5 times. One week after drug cessation, we obtained the coefficients of the main organs, serum biochemical parameters and the levels of gonadal hormones (T and E2), analyzed the pathological changes of the main organs by HE staining, observed sperm count, motility and abnormality under the microscope, and detected germ cell apoptosis by TUNEL.</p><p><b>RESULTS</b>Compared with the control, the low-dose (200 mg/kg) group showed no significant changes in the above parameters, while the high-dose (500 mg/kg) group exhibited a decrease in the coefficients of the liver, heart and kidneys, and a significant increase in such serum biochemical parameters as ALT, ALT/AST and BUN (P < 0.05). The high-dose group also showed significantly reduced sperm density and motility, increased sperm abnormality and germ cell apoptosis (P < 0.05), but no obvious pathological changes in the liver, kidney spleen, testis and epididymis.</p><p><b>CONCLUSION</b>Low-dose nanosized TiO2 has no obvious effect on male mice, but high-dose may significantly reduce their sperm count and function and induce germ cell apoptosis, although its damage on the liver and kidney function is slight.</p>