OBJECTIVETo study on the effects of sub-chronic exposures to high-frequency electromagnetic field (HF-EMF) on the estrous cycle, ovarian pathological changes and related hormones and preliminarily investigate the female genital toxicities of HF-EMF in rats.

METHODS60 Wistar female adult rats were randomly divided into five groups based on body weight and radiated with different levels of 30 MHz electromagnetic field (0, 25, 100, 400 and 1600 V/m) for eight hours daily. Weekly the rats were continuously exposed five days. From the 48th day the four stage of estrus cycle were observed with smear method of the vaginal cell. Fifty-six days later the serum levels of sexual hormones were detected with the radioimmunoassay on estrus stage. The constituent ratio of the distinct follicle number on ovaries were observed with the HE staining and the ultrastructure was observed with the transmission electron microscope. Meanwhile, the ovarian humid weight and organ coefficient were observed.

RESULTSThere was no significant difference in ovarian humid weight and organ coefficient between the exposure and the control groups. The time of proestrus in the 100 V/m group, the 400 V/m group and the 1600 V/m group was decreased significantly [(15.00 +/- 5.06), (11.40 +/- 2.05) and (10.56 +/- 0.96) h in the exposure group compared with (18.70 +/- 2.96) h in the control group, P < 0.01], and the time of Anestrum in the 400 V/m group and the 1600 V/m group were increased significantly [(101.20 +/- 17.81) and (115.33 +/- 19.28) h in the exposure group compared with (69.80 +/- 11.42) h in the control group, P < 0.01)]. Serum LH in the 400 V/m and 1600 V/m group was increased significantly [(11.02 +/- 1.11) and (14.70 +/- 1.94) mU/ml in the exposure groups compared with (8.70 +/- 0.53) mU/ml in the control group, P < 0.01], and serum E2 was decreased significantly [(57.16 +/- 31.56) and (50.57 +/- 25.16) pg/ml in the exposure groups compared with (95.04 +/- 32.62) pg/ml in the control group, P < 0.01]. The composition ratio of the corpus luteum/albicans number in the 400 V/m group and the 1600 V/m group was increased significantly (19.75% and 19.04% in the exposure groups compared with 14.01% in the control group, P < 0.05). The composition ratio of the atretic follicle number was increased significantly in the 100 V/m, the 400 V/m and the 1600 V/m group (8.45%, 9.95% and 11.70% in the exposure groups compared with 7.72% in the control group, P < 0.01). The composition ratio of the mature follicle and the pri/sec follicle was decreased significantly in the 400 V/m and the 1600 V/m group (1.50% and 1.55% in the exposure groups compared with 3.36% in the control group. 22.24% and 21.09% in the exposure groups compared with 26.60% in the control group, P < 0.01). Along with the increase of radiation dose, the ultrastructure of cell on the ovaries appeared more abnormal.

CONCLUSIONSThe toxicities of female gonads are closely associated with exposures to HF-EMF. The nonage damage of female gonadal toxicities might emerge on the ovaries.