Exposure temperature, but not donor age, is a confounding factor for in vitro translocation production by chronic irradiation.
OBJECTIVE
To assess the effects of incubation temperature during irradiation, and of donor age, on the in vitro induction of chromosomal translocations in human lymphocytes.


METHODS
Lymphocytes from six human male donors were scored, using fluorescence in situ hybridization, for the presence of chromosomal translocations involving chromosomes 1 to 6 after in vitro, chronic exposure (delivered continuously over 48 h at 37 degrees C or at 20 degrees C) to tritium beta-rays or 60Co gamma-rays.


RESULTS
No age-related difference in the alpha coefficients of the fitted induction curves was observed for gamma-ray-exposed lymphocytes obtained from four donors whose ages ranged from 24 to 79 years, or for tritium beta-ray-exposed lymphocytes from two donors aged 36 and 62 years. Duplicate samples from one donor, irradiated concurrently at 20 degrees C or 37 degrees C, gave significantly different alpha coefficients: 0.128+/-0.008 and 0.053+/-0.004, respectively (p<0.0001). The S-ratio (the ratio of induced complete to incomplete translocations) was found to be independent of radiation dose, donor age and exposure temperature.


CONCLUSIONS
For biodosimetry in chronic irradiation situations, the use of alpha coefficients derived from the dose-response curves of cells chronically irradiated in vitro at body temperature is recommended. With respect to induction rates, donor age does not appear to be a confounding factor. The S-ratio is independent of radiation doses, exposure temperatures, or donor ages.
Lucas
J N
JN
University of California, Lawrence Livermore National Laboratory, Livermore 94550, USA. lucas1@llnl.gov
Deng
W
W
Hsieh
W A
WA
Galvan
N
N
Gale
K L
KL
Morrison
D P
DP
D000328:Adult; D000367:Age Factors; D000368:Aged; D004249:DNA Damage; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008214:Lymphocytes / Q000528:radiation effects* / Q000648:ultrastructure; D008297:Male; D008875:Middle Aged; D012062:Relative Biological Effectiveness; D013696:Temperature; D014178:Translocation, Genetic / Q000528:radiation effects*