Influence of ara A on the formation of dicentrics in irradiated quiescent CHO cells.
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.
Virsik-Peuckert
P
P
Institut für Medizinische Physik und Biophysik, Universität, Göttingen, Germany.
Volkmer
B
B
Mehmel
D
D
D000818:Animals; D016466:CHO Cells; D002869:Chromosome Aberrations; D006224:Cricetinae; D004249:DNA Damage / Q000187:drug effects* / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects*; D004307:Dose-Response Relationship, Radiation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007399:Interphase; D019384:Nucleic Acid Synthesis Inhibitors; D013696:Temperature; D013997:Time Factors; D014740:Vidarabine / Q000494:pharmacology*; D014965:X-Rays
D004791:Enzyme Inhibitors; D019384:Nucleic Acid Synthesis Inhibitors; D014740:Vidarabine