Effects Of 17-β Estradiol On Estrogen Receptor Subtypes Expression In Early Or Late Menopause Mouse Aorta

ObjectivesTo investigate effects of 17-(3 estradiol on estrogen receptor subtypes expression changes in early or late menopause mouse aorta.MethodsThirty-two 10-month-old SD female mice were ovariectomized(OVX)for postmenopausal models.All menopausal rats were randomized into 2 groups by a random number table:early menopausal group(E group)and late menopausal group(L group).We defined the time of 3 days after OVX(E group)to approximate the initial stage of menopause for women and 4 months after OVX(L group)to approximate the advanced-stage of menopause for women respectively.Each group was divided into 2 groups:estrogen treatment group(Eovx+E2 group and Lovx+EZ group)and non-estrogen treatment group(Eovx group.Lovx group).All estrogen treatment groups were treated with 17-(3 estradiol by subcutaneous injection every other day for 1 month before euthanized.All non-estrogen treatment groups were treated with vehicle by subcutaneous injection every other day for 1 month before euthanized.Detect aortic estrogen receptor ERa,ERβ and changes of ERβ/ERa ratio in the four groups by immunohistochemical and real time quantitative polymerase chain reaction.ResultsImmunohistochemistry result:Lovx group shows a marked decrease of ERa and a slight increase of ERβ expression compared to Eovx group.ERβ/ERα ratio in Lovx group was slightly higher than Eovx group but no statistical significance was found.ER(3/ERα ratio in Lovx+Ez group showed a significant increase than Eovx+E2 group after meddling by E2.There was no significant change about ERβ/ERα ratio between Eovx group and Eovx+E2 group.However,ERβ/ERa ratio in Lovx+E2 group was significantly higher than those in Eovx+E2 group.Real Time Quantitative PCR result:Lovx group shows a marked increase of ER(3 mRNA compared to Eovx group.Besides that,Lovx+E2 group showed a significant increase than Eovx+E2 in ERβ mRNA expression.ConclusionsAging itself didn’t affect ERβ/ERα ratio in ovariectomized mice,but markedly alters estrogen-mediated effects on ERβ/ERα ratio.The results provide more evidences to the"Timing Hypothesis" of menopausal hormone therapy.