Oxygen effect and adaptive reactions of cells. Report 1. Adaptation to hypoxia associated with attenuation of its radioprotective effect. [. gamma. rays; mice]

In mice exposed to total-body radiation, the radioprotective effect of gas hypoxia (5 to 6% O/sub 2/ in a nitrogen and oxygen gas mixture) is at a maximum in the first 10 min after producing hypoxia, then diminishes sharply and remains stable for a long time. Evaluation was made on the basis of the criterion of survival rate, induction of chromosomal aberrations in bone marrow cells and reduction in number of endocolonies in the spleen of intact and urethane-anesthetized mice. The possible mechanisms of this phenomenon are discussed, with consideration of the dynamics of pO/sub 2/ drop in subcutaneous connective tissue.