Role of soy diet and L-arginine in cyclosporin-A-induced osteopenia in rats.

Our previous studies show that chronic administration of L-arginine decreases cyclosporin-A-induced bone loss. The present study was designed to investigate whether a soy diet could prevent cyclosporin A-induced osteopenia and eventually improve the protective effect of L-arginine. Rats on soy diet were treated with cyclosporin-A, L-arginine, cyclosporin-A + L-arginine or saline. Control groups received a normal diet and the same pharmacological treatment. Our results show that a soy diet prevents osteopenia only in the spinal cord (+30%) and confirm the protective effect of L-arginine in cyclosporin-A-induced osteopenia in whole body, pelvis and spine of rats on a normal diet (+31%, +55%, +55%, respectively). Moreover these data show that the osteoprotective effect of L-arginine in the whole body, pelvis and spine improves in the case of soy diet (+60%, +72%, +89%, respectively). The results suggest that a soy diet exerts a positive effect in cyclosporin-A-induced osteopenia only in sites with high turn-over and improves the osteoprotective effect of L-arginine.