ENERGY STATUS AND RADIOBIOLOGICAL HYPOXIA AT SPECIFIED OXYGEN CONCENTRATIONS

The relationship between energy status and oxygen concentration was evaluated using Chinese hamster ovary cells over a gas-phase oxygen concentration ranging from 40 to 210,000 ppm O2. Energy status was examined in cells in complete medium equilibrated with specified gas-phase oxygen concentrations, in the presence and absence of glucose. The change in two parameters of energy status, adenylate energy charge, which is ([ATP] + 1/2[ADP])/([ATP] + [ADP] + [AMP]), and ATP/cell as a function of oxygen concentration, was compared with the radiation oxygen enhancement ratio. In the presence of glucose, neither parameter of energy status is substantially affected by oxygen at various concentrations. In the absence of glucose, energy status is affected over the oxygen concentration range which parallels the change in the radiation oxygen enhancement ratio. However, the magnitude of the changes in energy status is dependent upon the duration of oxygen deprivation. In addition, glucose deprivation alone results in a decrease in ATP/cell in the presence of 210,000 ppm O2.