[Hypoxia and reoxygenation in experimental tumors]

Hypoxic fractions (HF) and reoxygenation of various murine tumors were studies using a paired survival assay. All irradiations were given to whole-body of mice without anesthesia or physical restraint, both of which can increase HF artificially. HF's of 4 different tumors of 1 cm in diameter were between 4.5% and 14%. Thus, variation of HF due to tumor type was quite small. HF was roughly correlated with tumor size and proportion of necrotic areas. Reoxygenation was examined in two tumor systems, and it occurred rapidly (within 1 hr after radiation) in one tumor but rather slowly in another.