Comparison of single-strand breaks in the DNA of rat thymocytes induced by irradiated histidine and. gamma. rays

Journal Article · Tue Mar 01 04:00:00 EST 1977 · Radiat. Res.; (United States)

DOI:https://doi.org/10.2307/3574664· OSTI ID:7215344

Ueno, A M; Matsudaira, H

Single-strand breaks in the DNA of rat thymocytes induced by ..gamma.. rays and irradiated histidine were studied using alkaline sucrose gradient centrifugation. ..gamma..-ray-induced DNA breaks were found to be random in nature with their number increasing linearly with increasing dose. These breaks were produced with an efficiency estimated to be 84.5 eV per break and were rejoined partially during postirradiation incubation. Treatment of the cells at 2/sup 0/C with irradiated histidine, however, produced the appearance of two distinct peaks of smaller DNA. The molecular weights of these species of DNA were estimated to be 3 to 4 x 10/sup 8/ and 6 x 10/sup 7/ daltons, respectively, compared to 6 x 10/sup 8/ daltons in untreated cells. Increasing the radiation dose given the histidine resulted in an increase in the proportion of the 6 x 10/sup 7/ daltons DNA species but failed to decrease further the molecular size. Posttreatment of ..gamma..-irradiated cells with irradiated histidine at 2/sup 0/C induced further breaks in the DNA. This phenomenon was not observed, however, when the radiation dosage exceeded 30 krad. Rejoining of induced breaks was not observed during incubation at 37/sup 0/C of irradiated histidine-treated cells. Treatment of the cells with three sulfhydryl-binding reagents produced results similar to those produced by irradiated histidine. Moreover, both irradiated histidine and sulfhydryl agents apparently inhibited the rejoining of ..gamma..-ray-induced DNA strand breaks. It is concluded that irradiated histidine and sulfhydryl-binding agents induce specific DNA breakage, possibly the dissociation of large DNA molecules into certain subunits. The possible involvement of sulfhydryl groups in the structure of cellular DNA of high molecular weight is discussed.

• Research Organization: National Inst. of Radiological Sciences, Anagawa, Japan
• OSTI ID: 7215344
• Journal Information: Radiat. Res.; (United States), Journal Name: Radiat. Res.; (United States) Vol. 69:3; ISSN RAREA
• Country of Publication: United States
• Language: English

Related Subjects

560121* -- Radiation Effects on Cells-- External Source-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINO ACIDS
ANIMAL CELLS
ANIMALS
AZOLES
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
CARBOXYLIC ACIDS
DNA
ELECTROMAGNETIC RADIATION
GAMMA RADIATION
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HISTIDINE
IMIDAZOLES
IONIZING RADIATIONS
MAMMALS
MOLECULAR WEIGHT
NUCLEIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
RADIATION EFFECTS
RADIATIONS
RADICALS
RADIOINDUCTION
RATS
RODENTS
SOMATIC CELLS
STRAND BREAKS
SULFHYDRYL RADICALS
THYMOCYTES
VERTEBRATES