Synergistic effect of genistein and zinc on bone components in the femoral-metaphyseal tissues of female rats.

The effect of genistein and zinc on bone components in rats was investigated. Femoral-metaphyseal tissues obtained from female rats (4 weeks old) were cultured for 24 h in a medium containing either vehicle or genistein (10(-7)-10(-5) M) in the absence or presence of zinc sulfate (10(-6)-10(-4) M) in vitro. The presence of genistein (10(-6) and 10(-5) M) or zinc (10(-6) and 10(-5) M) caused a significant increase in alkaline phosphatase activity, deoxyribonucleic acid (DNA), and calcium content in the metaphyseal tissues. These increases were significantly enhanced by the combination of each compound. The synergistic effect on bone components was seen in the combination with genistein (10(-6) and 10(-5) M) plus zinc (10(-5) M). Such an effect was completely blocked by the presence of cycloheximide (10(-6) M), an inhibitor of protein synthesis. Moreover, the oral administration of genistein (100 and 300 micrograms/kg body weight) or zinc sulfate (1 and 5 mg Zn/kg) to rats for 3 days caused a significant elevation of alkaline phosphatase activity, DNA, and calcium content in the femoral-metaphyseal tissues. These increases were significantly enhanced by the combination of each compound. The synergistic effect was seen in the case of genistein (100 and 300 micrograms/kg) plus zinc (5 mg/kg). These results demonstrate that the anabolic effect of genistein on bone components is synergistically enhanced by zinc in vitro and in vivo. This study further supports the view that the combination of nutritional factors has a potent anabolic effect on bone metabolism.