Exposure temperature, but not donor age, is a confounding factor for in vitro translocation production by chronic irradiation

Abstract

Purpose: To assess the effects of incubation temperature during irradiation, and of donor age, on the in vitro induction of chromosomal translocations in human lymphocytes. Material and 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°C or at 20°C) to tritium β-rays or 60Co γ-rays. Results: No age-related difference in the alpha coefficients of the fitted induction curves was observed for γ-ray-exposed lymphocytes obtained from four donors whose ages ranged from 24 to 79 years, or for tritium β-ray-exposed lymphocytes from two donors aged 36 and 62 years. Duplicate samples from one donor, irradiated concurrently at 20°C or 37°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.