Abstract: BACKGROUND AND AIM: To study the combined toxic effects of phoxim(Pho) and methomyl(Met) on reproductive function in male rats. MATERIALS AND METHODS: The adult SD rats were randomly divided into 4 groups (including a control and three treated groups).Various daily dose of Pho(1/50 LD50, 25.20 mg/kg), Met(1/50 LD50, 0.47 mg/kg), Pho＋Met(25.20＋0.47 mg/kg) were given to rats by gastric gavage for 60 successive days. 2×2 factorial analysis was used in the experiment. Body weight gain and organ weights were determined. Sperm counts, the spermatozoon survival rate and the aberration rate of the spermatozoon were measured. The activities of SOD, GST and the GSH and MDA level were ascertained in both serum and testiculer samples. The activities of ACP, LDH and ATP were assessed in testicular samples. The testosterone level was measured in serum samples and the histomorphology changes of testis and epididymis were examined. RESULTS: ① There was synergism between Pho and Met on the sperm counts, spermatozoon survival and aberration rates, as well as testosterone level. ② There was antagonism between Pho and Met on GSH level and the SOD activity in serum; on GSH level of SOD activity and GST in testicle as well as the activity of ACP and Na＋_K＋_ ATPase in testicle. ③ Testicular pathology showed shed spermatogenic cells in seminiferous tubules, the layers and counts of spermatogenic cell reduced and disordered cellular arrangement in testicular tissue. There was no pathological changes in the epididymis. CONCLUSION: Markedly increased toxic effect of the pesticide mixture was found on sperm counts, spermatozoon survival and aberration rates and testosterone level. The combined exposure to Pho and Met can produce enhaced toxic effects on reproductive function in male rats.

Key words: phoxim, methomyl, combined action, toxicity on male reproduction