title: Tumor radiation responses and tumor oxygenation in aging mice.
abstract: 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.
authors.affiliation: Yale University School of Medicine, Department of Therapeutic Radiology, New Haven, Connecticut 06510-8040.
authors.forename: S
authors.initials: S
authors.lastname: Rockwell
mesh_terms: D000367:Age Factors; D000818:Animals; D001802:Blood Substitutes / Q000494:pharmacology; D002460:Cell Line; D004338:Drug Combinations / Q000494:pharmacology; D005466:Fluorocarbons / Q000494:pharmacology; D006895:Hydroxyethyl Starch Derivatives; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism / Q000532:radiotherapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D010101:Oxygen Consumption; D011836:Radiation Tolerance; D014407:Tumor Cells, Cultured / Q000528:radiation effects
chemical_list: D001802:Blood Substitutes; D004338:Drug Combinations; D005466:Fluorocarbons; D006895:Hydroxyethyl Starch Derivatives; C017323:glucose, glycerol, hydroxyethyl starch, perfluorodecalin, perfluorotripropylamine, pluronic F-68, salts, yolk phospholipids drug combination