en Medical Physics Medical Physics تحقيق بديع Original Research <div style="text-align: justify;">Background: This work aimed at studying the protective effect of melatonin (MLT) against cypermethrin&nbsp;or &gamma;-radiation induced testicular damage. Material and Methods: Thirty six Male rats were randomly divided into 6 groups.&nbsp; Control group, group treated with MLT (10 mg/Kg b. wt.), group administered cypermethrin (25 mg/ kg. b. wt.), group 4 was exposed to fractionated whole body &gamma;-radiation (the sum=8 Gy), group 5 was co-administered with MLT (10 mg/Kg .b. wt.) and cypermethrin (25 mg/kg b. wt.) and finally group 6 rats were supplemented with MLT (10 mg/Kg .b. wt.) and subsequently administered&nbsp; fractionated &gamma;-radiation(the sum=8 Gy). After treatment for 29 successive days, all animals groups were investigated for hormonal assay, sperm quality, oxidative indices and histological examination of testicular tissues. Results: Rat&rsquo;s treatment with g-radiation or Cypermethrin showed a significant decrease in body weight, testis, epididymis, ventral prostate and seminal-vesicles weights. Also, a significant increase was observed in the levels of TBARS and H₂O₂, while a significant reduction occurred in the activity of SOD, CAT and GSH content in testis tissues, in addition to a significant decrease in testosterone hormone. On the other hand, a significant increase occurred in FSH and prolactin hormones .moreover, a significant decrease in sperm count and motility occured beside a significant increase in abnormal forms. Pretreatment of rats with MLT improved the disturbances induced in the tested parameters of rats either received cypermethrin or &gamma;-irradiation. Conclusion: According to the present findings, the ameliorative role of MLT is obvious against cypermethrin&nbsp;or &gamma;-irradiation induced testicular damage probably, due to its antioxidative properties.</div> Melatonin, Ionizing radiation, cypermethrin, antioxidants, testis, hormones. 765 776 http://ijrr.com/browse.php?a_code=A-10-2055-62&slc_lang=en&sid=1 E.M. Kamal El-Dein Kamal El-Dein 7900319475328460017384 7900319475328460017384 No Health Radiation Research Department, National Center for Radiation Research and Technology (NCRRT), Egyptian Atomic Energy Authority, Cairo, Egypt L.M. Anees Lobnaanis@gmail.com 7900319475328460017385 7900319475328460017385 Yes Health Radiation Research Department, National Center for Radiation Research and Technology (NCRRT), Egyptian Atomic Energy Authority, Cairo, Egypt