Effects of dimethylpyrazine isomers on reproductive and accessory reproductive organs in male rats.

The effects of dimethylpyrazine isomers on reproductive and accessory reproductive organs in male rats were studied. Following the administration of 2,5-dimethylpyrazine (100 mg/kg, s.c.) the weight of prostate and seminal vesicles, as well as testosterone levels in plasma were significantly decreased. One isomer of dimethylpyrazine, 2,6-dimethylpyrazine (100 mg/kg, s.c.), affected only the seminal vesicles, while 2,3-dimethylpyrazine had no influence on accessory reproductive organs. Following administration of 100 mg/kg of 2,5-dimethylpyrazine, acid phosphatase activity in the prostate and fructose content in the seminal vesicles were also significantly decreased compared with tissues from vehicle-treated animals. Weight of the testes and acid phosphatase activity therein were not affected following the administration of 2,5-dimethylpyrazine, nor were numbers of spermatozoa in the epididymis. These results showed that 2,5-dimethylpyrazine induced decrease in prostate and seminal vesicle weight by inhibiting testosterone uptake and reducing plasma testosterone levels.