Anabolic effect of daidzein on cortical bone in tissue culture: comparison with genistein effect.

The effect of daidzein on cortical bone in vitro was investigated. Femoral-diaphyseal tissues obtained from elderly female rats were cultured for 24 h in Dulbecco's modified Eagle's medium (high glucose, 4.5%) supplementation with antibiotics and bovine serum albumin. The experimental cultures contained 10(-7) to 10(-5) M daidzein. The presence of daidzein (10(-6) and 10(-5) M) caused a significant increase of alkaline phosphatase activity, deoxyribonucleic acid (DNA) and calcium contents in bone tissues. This effect was equal to that of genistein (10(-6) and 10(-5) M). Daidzein (10(-5) M) or genistein (10(-5) M)-induced increase of calcium content and alkaline phosphatase activity in bone tissues was completely prevented by cycloheximide (10(-6) M), an inhibitor of protein synthesis. Anabolic effect of daidzein and genistein on bone components was equal to that of 17beta-estradiol (10(-8) M). The effect of isoflavohoids was not enhanced by the addition of 17beta-estradiol. The combination of daidzein and genistein did not have an additive effect. These findings indicate that daidzein has an anabolic effect on bone metabolism in tissue culture in vitro, and that this effect is equal to genistein effect. Isoflavonoids may stimulate bone formation and mineralization.