EFFECTS OF PHYTOESTROGEN ON BONE LOSS IN OVARIECTOMIZED MICE.

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Genistein, an isoflavone abundantly present in soybeans, has structural similarity to estrogen, suggesting that genistein may act as a phytoestrogen. To examine the possible role of genistein in hemopoiesis and bone metabolism, female mice were either sham-operated or ovariectomized (OVX), and selected OVX mice were administered genistein for 2-4 weeks (0.1-0.7 mg/day) or 17β-estradiol (E2) (0.01-0.1 μg/day) subcutaneously, using a mini-osmotic pump. In OVX mice, uterine weight declined, but was completely restored by E2 administration. In contrast, genistein did not demonstrate a reversal of the OVX-induced uterine atrophy. The number of bone marrow cells markedly increased 2-4 weeks after OVX, and most of these were B220-weakly positive pre-B cells. The increased B-lymphopoiesis was completely restored not only by E2, but also by genistein administration. In OVX mice, the trabecular one volume of the femoral distal metaphysis, measured by mCT scanning and dual energy X-ray absorptiometry, was markedly reduced, and genistein restored this, as did E2. These results indicate that genistein exhibits estrogenic action in bone and bone marrow to regulate B-lymphopoiesis and prevent bone loss, without exhibiting estrogenic action in the uterus. Phytoestrogens may be useful estrogenic action in the uterus. Phytoestrogens may be useful for preventing bone loss due to estrogen deficiency in females.