PREVENTIVE EFFECTS OF THE PLANT ISOFLAVONES, DAIDZIN AND GENISTIN, ONBONE LOSS IN OVARIECTOMIZED RATS FED A CALCIUM-DEFICIENT DIET

The effects of the plant isoflavones, daidzin and genistin, on bone lo ss in ovariectomized (ovx) rats fed a calcium-deficient diet were inve stigated. Daidzin and genistin were orally administered to ovx rats fo r 4 weeks. The femurs of these rats showed significantly lower density , strength (breaking forces), ash weight and calcium and phosphorus co ntent (p<0.01) in comparison with those of sham-operated rats. These c hanges were largely prevented in animals receiving oral daidzin or gen istin for 4 weeks at a dose of 50 mg/kg/d and in animals receiving sub cutaneous estrone (7.5 mu g/kg/d) as a positive control. Ovariectomy c aused atrophy of the uterus and increased the ratio of the urinary exc retion of pyridinoline and deoxypyridinoline to endogenous creatinine excretion. This was prevented by administration of daidzin or estrone, but, interestingly, not genistin. The preventive effect of daidzin tr eatment on bone loss in ovariectomized rats appears to be due to suppr ession of bone turnover. Genistin has a different mechanism of action from daidzin.