| Objective To investigate the effect of the bone-targeted estrogen, rhein-estrone ( LC) , on the expression of ERαand ERβmRNA in the bone and uterine in ovariectomized rats.Methods Seventy-two 6-month Wistar female rats were randomly divided into 6 groups:Sham group ( Sham) , ovariectomized rat model group ( OVX) , estrone group ( E, OVX +estrone 1.0 mg/kg· d) , H-LC group ( OVX +rhein-estrone 1.0 mg/kg· d) , M-LC group ( OVX +rhein-estrone 0.5 mg/kg· d) , and L-LC group ( OVX +rhein-estrone 0.25 mg/kg· d) .Rats in all the groups except those in Sham group were bilaterally ovariectomized.After 24-week administration, the serum level of estradiol was detected using radioimmunoassay.The expression of ER αand ERβmRNA in bone and uterine was detected using reverse transcription polymerase chain reaction assay ( RT-PCR ) .Results Compared with that in Sham group, the serum level of estradiol in OVX group decreased significantly.When compared with that in OVX group, the serum level of estradiol increased significantly in E group, H-LC group, and M-LC group except in L-LC group. The expression of ERαmRNA and ERβmRNA in the proximal tibia of rats in Sham group was identified.The expression of ERβmRNA in OVX group was lower than that in Sham group, while no expression of ERαmRNA in OVX group was observed.The expression of ERαand ERβmRNA in E group showed no significant difference with that in Sham group.Compared with that in OVX group, the expression of ERβmRNA was up-regulated in all 3 rhein-estrone groups, but no expression of ERαmRNA was observed.No significant difference of the expression of ERβmRNA was observed among the rhein-estrone groups.The expression of ERαand ERβmRNA in the uterine was identified in Sham group.The expression of ERαmRNA in OVX group was lower than that in Sham group, while no expression of ERβmRNA in OVX group was observed.The expression of ERαand ERβmRNA in the uterine of rats in E group increased compared with that in OVX group.No significant difference of ERαmRNA expression was observed among the rhein-estrone groups, while a down-regulated expression of ERαmRNA was observed in all rhein-estrone groups when compared with that in Sham group and E group.Conclusion Rhein-estrone can selectively up-regulate the expression of ERβmRNA in the bone and the uterine , but show no effect on the expression of ERαmRNA.Estrone has no selectivity of both subtypes .This is a possible reason that rhein-estrone has protective effect on the bone , but shows no estrogen-like effect on the uterine in ovariectomized rats . |