Effects of estradiol on the expression of estrogen receptor in lens epithelial cell of castrated female Wistar rat

Background Recently researches indicated that estrogen plays important role in maintaining the normal metabolism of lens. Objective This study was to investigate the changes of estrogen receptor( ER ) α and β expressions in lens upon estrogen level in castrated female rat. Methods Sixty clean adult female Wistar rats were randomized into castrated group,sham operation group,ovariectomy group,ovariectomy with low-dose estradiol eyedropping group,ovariectomy with high-dose estradiol eyedropping group,ovariectomy with low-dose estradiol injecting group and ovariectomy with high-dose estradiol injecting group,and 10 rats for each.The castrated animal models were established by ovariectomy for 5 months.Then 50％,100％ oestradiol benzoate eyedrops were used 4 times per day respectively and 0.2 or 0.4 mg/kg oestradiol benzoate were intramuscularly injected at two-day interval for 6 weeks in corresponding experimental group.Serum estradiol concentration was detected in the rats of various groups at 5 months after ovariectomy and 6 weeks after administration of estradiol benzoate.The animals were sacrificed using the excessive anesthesia method and the lenses were obtained for the assay of ERα and ERβ expressions.The use of the animals complied with the Statement of ARVO. Results No obvious opacification of lenses and the changes of structure and morphology in lens were seen in the rats of various groups under the slit lamp microscope and light microscope during the observing duration after ovariectomy.The significant differences were found in serum estradiol concentrations among the 6 groups ( F=15490.527,P=0.000) or between before and after usage of estradiol benzoate( F=943.236,P =0.001 ).Six weeks after usage of estradiol benzoate,the expressions of ERα and ERβ in the lenses were lower in the castrated group,ovariectomy with high-dose estradiol eyedropping group and ovariectomy with low-dose estradiol injecting group compared with the the sham operative group (P＜0.05),but those in the ovariectomy with low-dose estradiol eyedropping group and ovariectomy with high-dose estradiol injecting group were elevated in comparison with above groups( P＜0.05 ),and expressions of ERα and ERβ in the lenses were similar to the sham operative group ( ERα:28.04±6.80 vs.31.30±7.11 ;ERβ:27.75±7.13 vs.25.38±5.59).Mean A values of ERα and ERβ in the lenses were lower in the castrated group,ovariectomy with high-dose estradiol eyedropping group and ovariectomy with low-dose estradiol injecting group compared with the sham operative group (P＜0.05),but those in the ovariectomy with low-dose estradiol eyedropping group and ovariectomy with high-dose estradiol injecting group were elevated in comparison with above groups ( P＜0.05 ),and mean 4 values of ERα and ERβ in the lenses were similar to the sham operative group (ERα:0.1833 ±0.0087 vs.0.1859 ±0.0067; ERβ:0.1689±0.0059 vs.0.1686±0.0095). Conclusions The expressions of ERα and ERβ in the LECs are associated with the level of serum estradiol.The effects of estrogen on lens were different by different medication way.Low-dose estradiol eyedropping was a more feasible approach to the prevention of cataract. Key words: Estradiol benzoate;  Estrogen receptor;  Apoptosis;  Lens;  Castrated rat model