Oxygen consumption of calvarial bone cells in vitro

Tissues with tortuous and narrow diffusion pathways and cells that are remote from blood vessels nonetheless can show high metabolic activity of which the underlying bases (transport mechanisms) are not fully understood. In one such bone tissue, the O2 consumption was measured by analyzing the decrease in the partial pressure of oxygen (Po2) in a closed chamber containing calvarial fragments from adult guinea pigs (250-400 g) or from neonatal rats and guinea pigs. The O2 consumption of fragments from adult guinea pigs amounted to 0.05, 0.066, and 0.095 ml/100 g* minute at 24, 27, and 36.5 degrees C, respectively. When the temperature exceeded 43 degrees C, O2 consumption irreversibly stopped. Both antimycin A and rotenone, which block the respiratory chain, reduced O2 consumption to approximately 20% of control values. O2 consumption was significantly higher in neonatal animals (0.369 ml/100 g* minute at 27 degrees C) and could be blocked completely by antimycin A. On the basis of the high consumption of O2 by bone cells, we hypothesize that specialized transport systems, i.e., gap junctions, are required to provide a sufficient supply of nutrients to cells in osseous tissue.