RESUMO
<p><b>OBJECTIVE</b>To explore the pathological characteristics and the dynamic change regularity of the testis induced by high power microwave (HPM) radiation.</p><p><b>METHODS</b>One hundred and sixty-five male Wistar rats were exposed to 0, 3, 10, 30 and 100 mW/cm2 HPM radiation for five minutes, and changes of testicular morphology and teratogenic ratio of epididymal spermatozoa were observed through light microscope and electron microscope at 6 h, 1, 3, 7, 14, 28 and 90 d after radiation.</p><p><b>RESULTS</b>Injury of testicular spermatogenic cells in rats might be induced by 3 to approximately 100 mW/cm2 HPM radiation, and the main pathological changes were degeneration, necrosis, shedding of spermatogenic cells, formation of multinuclear giant cells, decrease or loss of sperm and interstitial edema. Injury of spermatogenic cells underwent such phases as death and shedding, cavitation, regeneration and repair, characterized by being focalized, inhomogenous and phased. And the severity of pathological changes of the testis increased with power density. There was only scattered degeneration, necrosis, shedding of spermatogenic cells in the seminiferous tubule one day after 3 mW/cm2 radiation, and the pathological changes six hours after 10 mW/cm2 radiation was similar to those one day after 3 mW/cm2 radiation, but with the formation of multinuclear giant cells, and the above-mentioned pathological changes aggravated from one day to seven days after radiation. There was a significant increase in degeneration, necrosis, shedding of spermatogenic cells, as well as a significant decrease in spermatozoa and focal necrosis in simple seminiferous tubules six hours after 30 and 100 mW/cm2 radiation, and the subsequent changes were similar to those of 10 mW/cm2 radiation. There was a significant increase in teratogenic ratio of epididymal spermatozoa at 3 d, 1 to approximately 7 d, 6 h to approximately 7 d after 3, 10, 30 and 100 mW/cm2 microwave radiation respectively (P < 0.01 or P < 0.05).</p><p><b>CONCLUSION</b>HPM radiation may cause injury of testicular spermatogenic cells in rats, which has a positive correlation to radiation dosage and time.</p>