Abstract: Objective To study the effects of lactational exposure to bisphenol A(BPA) on the structure of testis and the expression of androgen receptor(AR) in testes of adult male mice.Methods Twenty pregnant female mice were randomly divided into 4 groups:high,medium and low BPA groups(BPA exposure at doses of 5,0.1,and 0.01 mg/kg/d),and a negative control group(corn oil).BPA was given daily by neck subcutaneous injection to the offspring male mice on postnatal day(PND) of 3-21.The offspring male mice were sacrificed on PND 70 and their body and testes weight were recorded.Sperm smears were made for counting sperm abnormality rate.Morphology changes of testes were detected with hematoxylin-eosin staining and the expression of AR was detected by immunohistochemistry and Western blot.Results The testis index of the adult mice was 0.44±0.018%,which was significantly lower than that of the control group(0.64±0.039%)(P<0.05),but there were no obvious changes in the medium and low BPA groups.The sperm abnormality rates in low,medium and high BPA group were 13.34±0.72%,16.41±0.67%,and 17.55±0.61%,which were all significantly increased compared to that of the control group(2.07±0.24%)(P<0.05).Testicular morphology observation revealed that the diameter of seminiferous tubules and the thickness of seminiferous epithelium decreased significantly(P<0.05).There were no obvious morphology changes in spermatogenic cells.The expression of AR in low,medium and high BPA group were 0.6642±0.0141,0.6363±0.0062,and 0.2938±0.2522,with significant increases(P<0.05).Conclusion Lactational exposure to BPA could induce obvious adverse effects on testis development including the increase of sperm abnormality rate,decrease of seminiferous tubules' diameter,thining of seminiferous epithelium,and the increase of AR expression in testis.