An apparent correlation between the inhibition of induced ornithine decarboxylase activity by ? radiation and the capacity for DNA repair synthesis in normal and ataxia telangiectasia human fibroblasts: No correlation with cell survival

Abstract

Exposure of normal human fibroblasts (F107) in stationary phase to gamma radiation inhibited the appearance of induced ornithine decarboxylase (ODC) activity. Skin fibroblasts derived from two ataxia telangiectasia (AT) patients (F184 and F182) displayed a similar response. The level of DNA repair synthesis was also similar in the three cell strains. Fibroblasts from another apparently normal donor (F196) were very sensitive to inhibition of induced ODC activity by gamma radiation and were also deficient in radiation-induced DNA repair synthesis. However, the two strains derived from normal donors displayed the same degree of cellular sensitivity towards X-rays, whereas the two AT strains showed the typical hypersensitivity to the cytotoxic effect of X-irradiation. The results suggest a possible correlation between the inhibition of induced ODC activity by gamma radiation and the extent of DNA repair synthesis at high radiation doses, but there is no correlation between these two parameters and cellular survival at low radiation doses.

Fractionated low-level gamma irradiation of Chinese hamster cells: Cellular and biochemical effects

“…This inhibition is due to DNA damage [6] and is correlated with the capacity for DNA repair synthesis [5]. The effect of 7 radiation on the appearance of induced ODC activity in cells exposed to fractionated irradiation is shown in Fig.…”

“…In addition two biochemical end points were measured: (a) the capacity for performing DNA repair synthesis; (b) the ability of acute radiation exposure to inhibit the transcriptionally-controlled induction of ornithine decarboxylase (ODC). The latter system was recently suggested as a probe for DNA repair capacity [4] and was shown to correlate with the capacity for DNA repair synthesis [5].…”