Fractionation of combined heat and radiation in asynchronous CHO cells. II. The role of cell-cycle redistribution

Journal Article · Thu Nov 01 04:00:00 EST 1979 · Radiat. Res.; (United States)

DOI:https://doi.org/10.2307/3575067· OSTI ID:5487702

Tomasovic, S P; Henle, K J; Dethlefsen, L A

Asynchronous Chinese hamster ovary (CHO) cells treated with conditioning hyperthermia (10 min at 45/sup 0/C) followed immediately by x irradiation with 4 Gy at room temperature display a decreased radiation response when either irradiated, or heated and irradiated again 24 h later. In addition, conditioning by 4 Gy of x radiation alone followed at 24 h by the combined heat and radiation treatment als resulted in a larger radiation D/sub 0/. Since the differential cell-cycle responses to heat- and x-ray-induced lethality are well established for CHO cells, the potential role of cell-cycle redistribution in the observed radiation desensitization was investigated by flow cytometry. At 24 h after the combined treatment, the fraction of the cells found in the G/sub 2/ + M portion of the DNA histograms was about three times that of the controls and there was a concomitant reduction in both the G/sub 1/ and S fractions. Similar observations were made after the conditioning heat treatment alone but cells irradiated with 4 Gy only did not display any marked redistribution at 24 h. A comparison of harsh acriflavin-Feulgen versus gentle mithramycin DNA-staining techniques as well as Ficoll centrifugation to remove dead and dying cells indicated that the DNA histograms generated at 24 h after conditioning heat and/or radiation represented the population present at the time of second treatment. Analysis of unsorted and sorted cells for mitotic figures and doublets indicated that the accumulated cells in the G/sub 2/ + M area of the histogram were in G/sub 2/. Comparisons of these cell-cycle redistributions to the observed alterations in radiosensitivity (D/sub 0/'s) lead to the conclusion that they are not directly related. Rather, the common parameters for alterations in sensitivity appear to be the initial radiation exposure combined with heat given simultaneously or 24 h later.

• Research Organization: Univ. of Utah, Salt Lake City
• OSTI ID: 5487702
• Journal Information: Radiat. Res.; (United States), Journal Name: Radiat. Res.; (United States) Vol. 80:2; ISSN RAREA
• Country of Publication: United States
• Language: English

Related Subjects

560120* -- Radiation Effects on Biochemicals
Cells
& Tissue Culture
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMAL CELLS
ANIMALS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BODY
BODY TEMPERATURE
CELL CYCLE
CELL DIVISION
CENTRIFUGATION
DNA
ELECTROMAGNETIC RADIATION
ENERGY
FEMALE GENITALS
FRACTIONATION
GONADS
HAMSTERS
HEAT
HYPERTHERMIA
IONIZING RADIATIONS
IRRADIATION
MAMMALS
MITOSIS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANS
OVARIES
RADIATION EFFECTS
RADIATIONS
RODENTS
SEPARATION PROCESSES
SYNERGISM
TEMPERATURE EFFECTS
VERTEBRATES
X RADIATION