Effects Of Exposure To Toluene On The Reproductive Endocrine In The Female Rats

Objective To study the effects of an subchronic exposure to toluene on estrous cyclicity, LH pulse and ovulation of female rats, on the ovaries and E2 and P. Our study would provide a scientific basis for reproductive endocrine toxicity of toluene and made more and more people realize the hazards of toluene so that the concentration of toluene in environment would be strictly controlled and people would refuse toluene abuse.Methods Beginning at 60 days of age, only females displaying 4 or 5 days estrous cycles were included in the experimental groups. 40 females were randomly divided into 4 groups and they were respectively gavaged with 0,35,70,330mg/kg toluene for 41 to 46 days. we examined the effects of toluene exposure on estrous cyclicity, LH pulse and ovulation of females. At 41 to 46 days, choosing rats which were in proestrus and collecting tail vein blood respectively at 12h, 15h, 18h and 21h.The serum were frozened until futher measurement of LH content. At 13h of vaginal estrus, after weighing and anaesthetizing, oocytes in the oviducts were collected and quantified under a dissecting microscope. Ovaries were weighed and placed in Bouin's liquid for 24h. Then we would make HE and TUNEL dyeing by which pathology changes of ovaries and apoptosis of granulosa cells were observed. The Abdominal aortic blood was collected in which the content of E2 and P was monitored by radioimmunoassay.Results (1) The 70mg/kg and 330mg/kg toluene groups had less feeding ,drinking and activities than the control and 35mg/kg groups. As toluene increased, the symptoms were more serious. (2) There was not a significant difference in the mean number of regular cycles, the days of proestrus, estrus and dioestrus during the 40-day period in the 35,70 mg/kg toluene groups compared to the controls(P>0.05). Between 330mg/kg toluene and controls ,there was a significant difference in the mean number of days in estrus(P=0.001), the regular cycles(P<0.001)and the rate of abnormal cycles(P<0.05). (3) In proestrus, the control females displayed an LH surge at 18h(9.30±0.98 mIU /ml). The concentration of this hormone was significantly decreased at 18h by administration of both 70mg/kg and 330mg/kg toluene (7.87±0.72,3.65±0.70 mIU /ml)(P<0.01).At 2100h, the LH concentration of 70mg/kg and 330mg/kg toluene groups were still significantly decreased as compared to the controls(P<0.05). (4) Examination of the oviducts on vaginal estrus revealed that 100% of the control and 35mg/kg group, 80% of 70mg/kg and 55.6% of330mg/kg had ovulated. Occurrence of ovulatory females had a significant difference in the 330mg/kg toluene group compared with controls.The number of oocytes in the 70mg/kg(11.13±2.23)and 330mg/kg(8.67±0.58) was significantly lower than the controls(14.30±1.42)(P<0.01).(5) The organ coefficients of ovaries were significantly lower in the 35 and 70 mg/kg toluene groups than in the controls(P<0.05).(6)Primordial follicles was almost similar in both experimental and control groups(P>0.05). Compared with controls, atretic follicles significantly increased, but developing follicles and corpora lutea prominently reduced in 70mg/kg and 330mg/kg toluene groups. In some females of 330mg/kg group, there were some mature antral follicles on the surface of ovaries.There was no clearly histopathological changes in ovarian follicles, but the corpora lutea had more abundant vacuoles and smaller volume and congestion in ovarian interstitial was more obvious as the concentration of toluene increased. (7)Apoptosis rate of ovarian granulose cells in 70mg/kg and 330mg/kg toluene groups was significantly higher than that in control group (P<0.001). (8) It was revealed that estradiol and progestin were significantly lower In 70mg/kg and 330mg/kg toluene groups than the controls,(P<0.01).Conclusion (1)Toluene made estrous cycles irregular which mainly manifested in persistent estrus.The possible reason was that toluene supressed preovulatory LH surge and made ovulation inhibit or delay.(2) Toluene had direct toxicity to ovary. For example, organ coefficient of ovary lowered, the number of developing follicles and corpora lutea reduced ,the volume of corpora lutea got small, abundant vacuoles were in luteal cells and congestion of ovarian interstitial was obvious.As the concentration of toluene increased, the toxicity was more serious.(3) Toluene could accelerate the apoptosis rate of ovarian granulose cells, which possibly lead to the increases of developing follicles and the reduces of atretic follicles.(4)Toluene made concentration of estradiol and progestin lower.