Changes in intrafollicular concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and hexanoyl-lysine adduct (HEL) during ovulation process. Immature (3 wks) rats received a subcutaneous injection of 20 units of pregnant mare serum gonadotropin (PMSG) to stimulate the multiple follicles. 48 hrs after PMSG injection, human chorionic gonadotropin (HCG) injection was performed to induce ovulation. The ovaries were quickly removed 0, 3, 6 and 9 hr after HCG injection and were transferred to the 500 μl of 0.01 M PBS buffer. Follicular fluids were collected by puncturing ovarian follicles with a 26-gauge needle under dissecting microscope and centrifuged at 300 g for 10 min, and the supernatants were collected and stored at -80C until assay. 8-OHdG and HEL concentrations were measured using ELISA kit. Data are shown as the mean ± SEM for 4 rats. *: p < 0.05 versus 0 h, 3 h.