Effects Of Zearalenone On Ovarian Development Of Weaned Piglets

Zearalenone(ZEA)exists in moldy sorghum,wheat,corn and other crops.Cereals and fodder products all over the world are widely contaminated with ZEA.ZEA has strong reproductive toxicity.ZEA can affect the growth and development and lead to reproductive obstacles in animals,which will bring huge economic losses to animal husbandry.In order to disclose the effect of ZEA on ovarian development of weanling piglets,the changes of the ovarian tissue structure and the expressions of indexes related to development(PCNA,Bcl-2,Bax,GHR and Hsp70)were investigated.It provided theoretical basis and ideas for the research of reproductive toxicity mechanism of ZEA and provided solutions of reproductive obstacles in pig production.In this experiment,21-25 days old weanling female piglets were selected as the research object.The histological changes of ovarian tissues were observed by HE staining.Immunohistochemistry,qRT-PCR and Western blot were used to compare the distribution and expression of PCNA,Bcl-2,Bax,GHR and Hsp70 in the ovaries of the weaned piglets after feeding different levels of ZEA(0.5,1 and 1.5mg/kg).The main results are as follows:(1)ZEA caused the changes in the tissue structure of the ovary in piglets and promoted the development of follicles.It was found that follicles developed abnormally in advance after treatment with different levels of ZEA by HE staining.The primordial follicles were significantly reduced,the growth follicles increased significantly and the follicles volume increased.The follicular development was the best at the dose of 1.0mg/kg,the growth follicles went atresia at the dose of 1.5mg/kg.(2)ZEA led to an abnormal proliferation in follicles by inducing up-regulation of PCNA in the ovaries.Through immunohistochemical localization of PCNA in the ovary,it was found that PCNA immunoreactivity was enhanced after ZEA treatment.The number of positive cells was the highest at the dose of 1.0mg/kg,which suggested that the follicles were highly proliferating.The results of qRT-PCR and Western blot detections showed that the expression of PCNA mRNA and protein in the ovary increased after ZEA treatment,which suggested thatZEA induced up-regulation of PCNA and promoted the abnormal growth of ovarian follicles.(3)ZEA induced abnormal expression of Bcl-2 and Bax in the ovary and led to abnormal development of ovarian follicles.The localization of Bcl-2 and Bax in the ovary by immunohistochemistry showed that the Bcl-2 immunoreactivity decreased and the Bax immunoreactivity increased after ZEA treatment.qRT-PCR and Western blot results showed that the expression of Bax mRNA and protein increased,which the expression of Bcl-2mRNA and protein decreased in a dose-dependent manner after ZEA treatment.The results suggested that ZEA induced abnormal expression of Bcl-2 and Bax in the ovary,leading to abnormal ovarian follicular development.(4)ZEA led to an advanced development of follicles by inducing up-regulation of GHR in the ovary.Through immunohistochemical localization of GHR in the ovary,it was found that the intensity of GHR immunoreactivity was enhanced after ZEA treatment.It is suggested that ZEA promoted ovarian follicle development.The detection results of qRT-PCR and Western blot showed that the expression of GHR mRNA and protein increased after ZEA treatment,which proved that ZEA induced up-regulation of GHR and promoted ovarian follicular development in advance.(5)ZEA caused stress in piglets and induced up-regulation of Hsp70 expression in the ovary,resulting in abnormal development of follicles.Through the immunohistochemistry localization of Hsp70 in the ovary,it was found that the Hsp70 immunopositive intensity was enhanced after ZEA treatment.It is suggested that ZEA caused piglet stress.The results of qRT-PCR and Western blot detections showed that the expression of Hsp70 mRNA and protein increased after ZEA treatment.It is suggested that ZEA caused piglet stress and induced Hsp70 up-regulation,leading to abnormal development of follicles.In conclusion,the results of this experiment showed that the weaning piglets' ovarian follicles developed in advance and large doses caused follicles to atresia after adding different levels of ZEA(0.5-1.5mg/kg)in the diet.ZEA promoted abnormal development of ovarian follicles and produced reproductive development toxicity by inducing abnormal expressions of PCNA,Bcl-2,Bax,GHR and Hsp70 in weaned piglets.