Modification by anisotonic treatment of repair and fixation of radiation damage in cell killing and transformation.

Anisotonic treatment of V79 cells after irradiation resulted in extensive fixation of potentially lethal damage (PLD). Fixation of PLD occurred more rapidly when treated with 1.5 mol l-1 NaCl than with 0.05 mol l-1 NaCl. These effects were further enhanced when cells were held at 0 degree C instead of 37 degrees C during irradiation. When the X-ray (10.0 Gy) and salt treatments were separated by incubation at 37 degrees C, survival increased rapidly by a factor of 2000, while repair of PLD in cells held in a plateau phase after X-rays (10.0 Gy) caused survival to increase four-fold. The data indicate that these mammalian cells sustain and repair a much larger amount of PLD than is measured by the conventional method of holding cells in a non-progressing state after irradiation. Radiation sensitivity in cells was modified by BrdUrd incorporation into cellular DNA or exposure to DMSO during irradiation. For these cells, fixation of damage by post-irradiation anisotonic treatment proceeded at the same rate for BrdUrd-treated cells, and at a diminished rate for DMSO-treated cells, compared with cells irradiated in the absence of these compounds. In C3H-10T 1/2 cells, post-irradiation anisotonic treatment (with 0.05 or 1.5 mol l-1 NaCl) also resulted in fixation of PLD and a rapid recovery when the X-ray and salt treatments were separated by incubation at 37 degrees C. Treatment with 0.05 or 1.5 mol l-1 NaCl solutions immediately after irradiation also resulted in elevated transformation frequencies, which increased with exposure time to anisotonic solutions.(ABSTRACT TRUNCATED AT 250 WORDS)