Rejoining of DNA Single-strand Breaks in Mammalian Cells Incubated in Buffer or in Medium after Aerobic or Anaerobic X-irradiation

Abstract

Using the sucrose-gradient centrifugation technique, the capacity of Chinese hamster ovary cells to rejoin DNA single-strand breaks when incubated in either a buffered salt solution or culture medium was studied after X-irradiation under air and N2. The initial rate of rejoining was about the same for cells incubated in buffered salt solution or in growth-medium. After doses which resulted in approximately the same initial yield of breaks, i.e., 4.7 and 18.8 krad for air and N2, respectively, the rate of rejoining of DNA single-strand breaks within the 1st 10 min of aerobic incubation was somewhat slower for cells irradiated under N2 vs. air. After the initial rapid rate of rejoining, a slower rejoining rate was discernible for medium-incubated cells. This slow process could not be studied for cells incubated in buffered salt solution due to buffer-induced DNA breakdown.