Abstract: Objective To explore the effects of arsenic exposure before sexual maturity on uterus,ovarian structure and sex hormone levels in female Sprague-Dawley(SD)rats.Methods Forty female SD rats were randomly divided into four groups:a control group with double-distilled water and three groups exposed to 1.25,2.5,and 5 mg/kg sodium arsenite (NaAsO₂) by gavage once a day for four weeks.At the end of the treatments,all the rats were decapitated.Cell morphological changes of ovary and uterus were observed with hematoxylin-eosin (HE)staining; serum follicle-stimulating hormone (FSH;),luteinizing hormone (LH),estradiol (E2),and progesterone(P)were assessed with radioimmunoassay(RIA)and serum vascular endothelial growth factor (VEGF),cyclin D1 and progesterone receptor(PR)were detected with enzyme-linked immunosorbent assay(ELISA).Results Decreased quantity of follicles and mature follicle with maldevelopment,atrophy,decreased glandular cavity,shortened glandular epithelium cells,and widened intercellular matrix in endometrium of the rats with arsenic exposure were observed.Compared to the rats of the control group,the rats with moderate and high NaAsO₂ exposure showed significantly decreased levels of FSH (3.23±0.20 and 3.21±0.18 IU/L),LH (2.64±0.27 and 2.62±0.25 ng/mL),E2 (56.69±6.37 and 55.95±7.25 pg/mL),VEGF (13.54±1.98 and 12.44±2.06 ng/L),cyclin D1 (1.089±0.133 and 1.040±0.136 μg/L),and PR (324.27±19.77 and 320.46±18.01 ng/L)(P<0.05 for all).Conclusion Exposed to arsenic before sexual maturity could result in structural changes in uterus and ovarian in SD rats and the effects may relate to the reduced serum levels of E2,LSH,and LH.