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Exp Gerontol. 1989;24(1):37-48.

Tumor radiation responses and tumor oxygenation in aging mice.

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Yale University School of Medicine, Department of Therapeutic Radiology, New Haven, Connecticut 06510-8040.


EMT6 mouse mammary tumors transplanted into aging mice are less sensitive to radiation than are tumors growing in young adult animals. We hypothesized previously that this reflected a greater proportion of radiation resistant, hypoxic cells in the tumors of aging animals. The experiments reported here compare the radiation dose-response curves defining the survivals of tumor cells in aging mice and in young adult mice. Cell survival curves were assessed in normal air-breathing mice and in mice which had been asphyxiated with N2 to produce uniform hypoxia throughout the tumors. Analyses of these survival curves revealed that 41% of the viable malignant cells were severely hypoxic in tumors in aging mice, while only 19% of the tumor cells in young adult animals were radiobiologically hypoxic. This did not appear to reflect anemia in the old animals, as the hematocrits of young and aging tumor-bearing animals were similar. Treatment of aging animals with a perfluorochemical emulsion plus carbogen (95% O2/5% CO2) increased the radiation response of the tumors, apparently by improving tumor oxygenation and thereby decreasing the number of severely hypoxic, radiation resistant cells in the tumors.

[Indexed for MEDLINE]

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