| Objective: To investigate the protective effects and mechanism of estrogen on lens, to provide the theoretic foundation and experimental evidence for new means of prevention and therapy on cataract.Methods: Thirty-two femal Sprague-Dawley rats were randomly divided into four groups: normal, ovariectomy, ovariectomy with estradiol replacement therapy, ovariectomy with estradiol and progest- erone replacement therapy. After 2 weeks of operation, each group was given 30% naphthalene (0.5 g/kg body weight, twice a week ) for 6 weeks through a stomach tube. The changes of lenses were observed with naked eye and slit-lamp microscope. After 6 weeks of naphthalene administration, all rats were skilled and serum estradiol and progesterone levels were determined with radioimmunoassay in each rat. The rats lenses were taken out to observe the cell morphological changes under the light microscope .The thickness of lens fiber and was measured under the scanning electron microscope, while the levels of lens oxidative defense system and soluble protein were examined with biochemical technique, the expression of estrogen receptor α and β, Bcl-2, Bax and P53 gene protein were observed with SP imunohistochemical technique. Results: 1.Under the slit-lamp microscope, there were different vacuoles, clefts or punctate opacity on lenses found in every group, but there were no significiant differences on the numbers of lenses among four groups. 2.Under the light microscope and transmission electron microscope, showed serious injury in morphology and structure of cell and tissue compared with normal group, but expressions in estradiol group, estradiol and progesterone group were similar to those in normal group. 3. Under the scanning electron microscope , the thickness of lens fiber in ovariectomy group was larger than in normal group(p<0.05) , the numbers among lens fiber was less than in normal group(p<0.01),but both of them in estradiol group, estradiol and progesterone group were showed the similar results to normals. 4. In examination of lens antioxidative defense system and soluble protein, the level of MDA in ovariectomy group increased as compared with other groups, while the levels of SOD, GSH, VitC and solubce protein were lower than other groups(p<0.05),there were no significiant differences among normal,estradiol, estradiol and progesterone groups. 5. In imunohistochemical examination, the expression of ERα, ERβ and Bcl-2 in ovariectomy group were less than normal, estradiol, estradiol and progesterone groups, but Bax and P53 expressed more than in other groups(p<0.05). The expressions of ERα, ERβ, Bcl-2, Bax and P53 among normal, estradiol, estradiol and progesterone were similar. 6. The level of serum estradiol and progesterone in ovariectomy group decreased significiantly as compared with normal group (p<0.01);but estradiol, estradiol and progesterone groups expressed similarly to normal group, and there was no significiant difference among estradiol , estradiol and progesterone groups.Conclusion: 1. Estrogen can increase resistance of naphthalene administrated rats and reduce toxic injury on lens cells and tissue through keeping normal level of antioxidative defense system to maintain transparency of lens. 2. Estrogen can downregular Bax and P53, upregular of Bcl-2 gene protein expression to reduce apoptosis of lens eipthelial cells and prevent opacity of lens. 3.In naphthalene administrated rats, anti-apoptosis may be one of mechanism besides antioxidation. 4.The protective effect on lens may be performed through ERαand ERβ, the direct and receptor-mediated pathway may be of great importance. 5. Progesterone does not influence expression of ER, Bcl-2, Bax and P53 on lens,estrogen associate with progesterone replacement therapy does not influence antioxidation and anti-apoptosis. But this result must be confirmed by futher experimental study and clinical observation.
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