Influence of ara A on the formation of dicentrics in irradiated quiescent CHO cells

• Published in: International journal of radiation biology Vol. 68; no. 3; p. 235
• Main Authors: Virsik-Peuckert, P, Volkmer, B, Mehmel, D
• Format: Journal Article
• Language: English
• Published: England 1995
• Subjects: Animals; CHO Cells; Chromosome Aberrations; Cricetinae; DNA Damage - drug effects; DNA Damage - radiation effects; DNA Repair - drug effects; Dose-Response Relationship, Radiation; Enzyme Inhibitors - pharmacology; Interphase; Nucleic Acid Synthesis Inhibitors; Temperature; Time Factors; Vidarabine - pharmacology; X-Rays
• ISSN: 0955-3002
• DOI: 10.1080/09553009514551161

CHO K1-cells, arrested in G0/G1 phase were irradiated with graded doses of 150-kV X-rays, and the dicentric chromosome aberrations in the first metaphase after reincubation in full growth medium were evaluated. When 500 microM ara A was administered at least 1 h before irradiation, maximal enhancement of the dicentric yield was obtained under 'immediate plating' conditions as well as under 'delayed plating' conditions, and under both conditions only the linear component alpha D of the aberration yield was affected. Since ara A had no effect upon the number of induced dsbs, as measured with PFGE at doses up to 100 Gy, the action pathway of ara A is suggested to be the repair/misrepair process manifested in the linear component of the dicentric yield. By varying the time at which either ara A at 37 degrees C was administered before irradiation or ara A at 4 degrees C was added after irradiation, it was observed that the repair step sensitive to ara A was completed within about 5 min after irradiation. This is in agreement with other observations of ara A action upon a fast repair step. The conversion of DNA single-strand breaks or base damage sites into double-strand breaks as a consequence of polymerase beta inhibition by ara A would explain the present results.