Polyfunctional radiosensitizers: VI. Dexamethasone inhibits shoulder modification by uncharged nitroxyl biradicals in mammalian cells irradiated in vitro

Journal Article · Sat Oct 01 04:00:00 EDT 1983 · Radiat. Res.; (United States)

DOI:https://doi.org/10.2307/3576175· OSTI ID:5427927

Millar, B C; Jenkins, T C; Fielden, E M; Jinks, S

Overnight exposure of Chinese hamster cells (V.79-753B) in vitro to 1 ..mu..g/ml dexamethasone increases the radiation resistance of the cells by about 20% both in air and in hypoxia, while having no appreciable effect on the oxygen enhancement ratio (OER). This is accompanied by substantially higher levels of glutathione. When dexamethasone-treated hypoxic cells are irradiated in the presence of nitroxyl biradicals there is no effect on the slope ratio of the exponential portion of the survival curves. In the case of uncharged biradicals, Ro.03-6061 and RSU-4072, which have been shown to modify the shoulder region of the hypoxic cell survival curve, there is an increase in extrapolation number in dexamethasone-treated cells. When hypoxic cells are exposed to the charged biradical RSU-4073, which does not exhibit shoulder modification, there is no change in extrapolation number. Experiments to examine the effect of concentration of these compounds on radiosensitization show that lower concentrations of both RSU-4072 and RSU-4073 are required to mediate changes in the slope of the hypoxic cell survival curve than to mediate shoulder modification, in the case of RSU-4072. Quantitative ESR data comparing the uptake of RSU-4072 and RSU-4073 with the monoradical TMPN into cells suggest that the cell membrane may act as a barrier to the incorporation of biradicals, and that this is greater for charged than for uncharged compounds. Treatment of cells with dexamethasone does not affect the uptake of the compounds.

• Research Organization: Inst. of Cancer Researc, Sutton, Surrey, England
• OSTI ID: 5427927
• Journal Information: Radiat. Res.; (United States), Journal Name: Radiat. Res.; (United States) Vol. 96:1; ISSN RAREA
• Country of Publication: United States
• Language: English

Related Subjects

550300 -- Cytology
560121* -- Radiation Effects on Cells-- External Source-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ADRENAL HORMONES
ANIMAL CELLS
ANIMALS
ANOXIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CELL CONSTITUENTS
CELL CYCLE
CELL KILLING
CELL MEMBRANES
COBALT 60
COBALT ISOTOPES
CORTICOSTEROIDS
DEXAMETHASONE
ELECTROMAGNETIC RADIATION
GAMMA RADIATION
GLUCOCORTICOIDS
HAMSTERS
HORMONES
HYDROXY COMPOUNDS
IN VITRO
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IONIZING RADIATIONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KETONES
MAMMALS
MEMBRANES
MINUTES LIVING RADIOISOTOPES
NITROXYL RADICALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXYGEN ENHANCEMENT RATIO
PREGNANES
RADIATIONS
RADICALS
RADIOINDUCTION
RADIOISOTOPES
RADIOSENSITIVITY EFFECTS
RODENTS
STEROID HORMONES
STEROIDS
SURVIVAL CURVES
VERTEBRATES
YEARS LIVING RADIOISOTOPES