Cultured cells from a severe combined immunodeficient mouse have a slower than normal rate of repair of potentially lethal damage sensitive to hypertonic treatment.
The effects of hypertonic 0.5 M NaCl treatment after irradiation on the repair of DNA damage were examined in fibroblasts of the severe combined immunodeficient (scid) mouse. These cells are hypersensitive to ionizing radiation because of a deficiency in the repair of double-strand breaks. Hypertonic treatment caused radiosensitization due to a fixation of potentially lethal damage (PLD) in scid cells, demonstrating that scid cells normally repair PLD. To assess the kinetics of the repair of PLD, hypertonic treatment was delayed for various times after irradiation. Potentially lethal damage was repaired during these times in isotonic medium at 37 degrees C. It was found that the rate of repair of PLD was much slower in scid cells than in BALB/c 3T3 cells, which have a "wild-type" level of radiosensitivity. This fact indicates that the scid mutation affects the type of repair of PLD that is sensitive to 0.5 M NaCl treatment. In scid hybrid cells containing fragments of human chromosome 8, which complements the radiosensitivity of the scid cells, the rate of repair was restored to a normal level. An enzyme encoded by a gene on chromosome 8 may also be connected with PLD which is sensitive to hypertonic treatment.
Kimura
H
H
Department of Experimental Radiology, Shiga University of Medical Science, Japan.
Terado
T
T
Komatsu
K
K
Nozawa
A
A
Ikebuchi
M
M
Aoyama
T
T
D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D004249:DNA Damage; D004260:DNA Repair; D051379:Mice; D016513:Mice, SCID; D011836:Radiation Tolerance; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*
D012462:Saline Solution, Hypertonic