Abstract：Estrogen plays an important role for mammalian in interim physiology period. The objective of this study was to reserch the effects of estradiol (E2) on cells proliferation and antioxidation in vitro bovine(Bos taurus) mammary epithelial cells (BMEC). Experimental groups were divided intoⅠ~Ⅴ, which were treated with E2 at 0.5, 1, 5, 10 and 100 nmol/L, respectively, the control group(CK) received the vehicle only. After culturing for 4, 8 and 12 h, the viability of mammary epithelial cells was assessed by MTT assay. The 12 h culture medium and cells were used to determin the content of malonaldehyde(MDA), the activities of Lactate dehydrogenase (LDH) and superoxide dismutase (SOD) by colorimetric method. HSP70(heat shock protein 70) mRNA expression were assayed by Real-time fluorescent quantitative PCR. The results showed: (1) Compared with the control group, Ⅰ~Ⅲ E2-treated groups showed markedly increased cell viabilities (P<0.05). ⅣandⅤE2-treated groups decreased cell viabilities. (2)Ⅰ~Ⅳ E2-treated groups showed a decrease in LDH activity in culture medium, HSP70 mRNA expression and SOD activity were significantly higher than those in the control group(P<0.05) but lipid reaction was reduced.ⅤE2-treated group showed a significant increase in LDH activity in culture medium(P＜0.05), a decrease of HSP70 mRNA expression and SOD activity (P<0.05) but lipid reaction was enhanced. The conclusion of this study: Low concentrations (0.5, 1.0 and 5.0 nmol/L) E2 could promote the proliferation of mammary epithelial cells, induced expression of HSP70 mRNA, which might play antioxidant role by increasing intracellular SOD activity. High concentration (100 nmol/L) of E2 could attenuate the proliferation and antioxidation of mammary epithelial cells, causing cell damage with long-term stimulation. This study provided some theoretical basis that exogenous estrogens can increase the antioxidant activity of bovine mammary tissue.
