Abstract
Serum-free bone-forming organ culture system using twenty-day fetal rat parietal bones was established. The effects of insulin on bone formation were studied in this system. Bones were cultured on grids and placed on a rocking platform under an aerobic condition. This condition increased the bone-forming activities of cultured rat parietal bones. The calcium content, dry weight of bone, and lactate produced by bone tissue in the medium were measured to study the precise bone-forming process of vital bones. Using this improved bone-forming organ culture system, insulin increased calcium content and dry weight of bone. These effects were maximum in bones treated with insulin at 10-6M. Histomorphometrical analysis showed that the areas of mineralized bone and bone matrix increased, and that many osteoblasts and few osteoclasts appeared in bones treated with insulin at 10-6M or higher. Insulin inhibited the release of 45Ca into the medium. From these results, it was suggested that insulin has a stimulatory effect on bone formation, enhancing both bone mineralization and bone matrix formation.
