The effects of hyperoxia upon bone in organ culture.

Hyperoxia has been reported to stimulate both resorption and synthesis of bone in vitro. The effects of increased oxygen tension were re-investigated using calvaria from infant mice maintained in a stationary grid culture system for 48 48 hours with an unsupplemented chemically defined medium. Resting resorption due to osteoclastic activity was demonstrated in the explants in air by Von Kossa staining, histology, and 45 Ca release. Resorption was inhibited by exposure to 95 per cent oxygen or hyperbaric oxygenation at 2 atmospheres pressure. Hyperoxia also depressed new bone formatin by osteoblasts although the production of a new collagen, as measured by the incorporation of 3H-proline, was greater in calvaria cultured in hyperbaric oxygen than in paired explants in 95 per cent oxygen. Thus hyperoxia was toxic for both synthetic and resorptive activity of bone cells; these effects may stem from the loss of vital factors present in natural MEDIA supplements.