The Preliminary Research Of The Ovarian Function Influence By Deltamethrin In Rat

Deltamethrin(DLT) is a synthetic pyrethroids which is low toxicity and widely used in agricultural and residential pest control.DLT is an endocrine-disrupting chemical and has estrogen-like activity:long-term exposure with it at low dose will produce reproductive toxicity.As the main reproductive and endocrine organs of female mammals,the ovary is mainly used to steroidogenesis and ovulation,which are closely regulated by follicular development.Studies have reported that DLT has toxic effects on the ovary of insects,but the effect of DLT on the ovarian function of mammals has not been studied.Therefore,this study investigated the effect of DLT on follicular development and steroidogenesis in the ovary of rats.Firstly,prepuberal female Sprague-Dawley rats were intragastric administration with 0,6.25 and 12.50mg/kg/d DLT for 7 days.After collecting the ovaries,we observed that the quality and size of the ovaries were significantly decreased after DLT treatment.The follicles are composed of oocytes,granulosa cells and theca cells,and can be divided into four stages according to their developmental status:primordial follicles,primary follicles,pre-antral follicles and antral follicles.We performed ovarian sections and HE staining and found that compared with the control group,the number of primordial or primary stage follicles and total follicle numbers were not significantly different in all treatment groups,but the number of antral follicles were reduced with a concomitant increase in pre-antral follicles in DLT treatment groups,suggesting that DLT inhibits pre-antral follicles develop to antral follicles.Anti-Mullerian hormone(AMH)is a paracrine factor that suppresses follicle recruitment in the ovary,and studies have shown that AMH inhibits the development of pre-antral follicles into antral follicles.So we used Immuno-histochemistry to detect the expression of AMH in ovarian tissues,and found that compared to the control group,the expression of AMH in the experimental group significantly increased a dose-dependent manner,suggesting that DLT may inhibit the development of pre-antral follicles to antral follicles by promoting the expression of AMH.Estrogen and progestin are major steroid hormones in ovary and are important for follicular development and normal female reproductive function.17β-estradiol is the most active estrogen in the female reproductive system,and progesterone is the main active form of progestin.We used electro chemiluminescence immuno assay to detect the secretion of estradiol and progesterone in the serum of rats,found that the level of estradiol was significantly increased and the level of progesterone was significantly decreased.Subsequently,Western blot was used to detect the synthesis of three key enzymes of steroidogenesis in ovarian tissue,including the expression levels of steroidogenic acute regulatory protein(StAR),cytochrome P450scc enzyme(P450scc)and aromatase were all significantly increased.To further clarify the effect of DLT on steroidogenesis in granulosa cells,we isolated primary granulosa cells from prepuberal female Sprague-Dawley rats,treated with 0,100,200 and 300μM of DLT for 48 hours.CCK-8 was used to detect primary granulosa cells viability with DLT treatment,the result showed that cell viability was significantly increased in a dose-dependent fashion.Using electro chemiluminescence immunoassay to detect the secretion of estradiol and progesterone in the supernatant of cells,found that the level of estradiol was significantly increased and the level of progesterone was not significantly changed after DLT treatment.Subsequently,Western blot was used to detect the expressions of the key enzyme of steroidogenesis in granulosa cells:StAR,P450scc and aromatase.We found that DLT treatment all significantly increased the expression of StAR,P450scc and aromatase.Studies have found that silent information regulator 1(Sirtl)can promote the synthesis of progesterone and estradiol and the expression of its key enzymes StAR and aromatase,and inhibit granulosa cell apoptosis.We used Western blot to detect the expression of Sirtl in ovarian tissues and primary granulosa cell,and found that the expression of Sirtl was significantly increased in a dose-dependent.In conclusion,using the model of prepuberal rats and primary granulosa cells,we found that DLT acute exposure inhibited the development of pre-antral follicles to antral follicles and altered steroidogenesis,which may be related to the increased expression of AMH and the key enzymes of steroidogenesis StAR,P450scc and aromatase.