Abstract
Health effects of tritium, a β-emitter and a by-product of the nuclear industry, is a subject of significant controversy. This mouse in vivo study was undertaken to monitor biological effects of low level tritium exposure. Mice were exposed to tritiated drinking water (HTO) at 10 KBq/L, 1 MBq/L and 20 MBq/L concentrations for one month. The treatment did not result in a significant increase of apoptosis in splenocytes. To examine if this low level tritium exposure alters radiosensitivity, the extracted splenocytes were challenged in vitro with 2 Gy γ-radiation, and apoptotic responses at 1 and 24 h were measured. No alterations in the radiosensitivity were detected in cells from mice exposed to tritium compared to sham-treated mice. In contrast, low dose γ-irradiation at 20 or 100 mGy, resulted in a significant increase in resistance to apoptotic cell death after 2 Gy irradiation; an indication of the radioadaptive response. Overall, our data suggest that low concentrations of tritium given to mice as HTO in drinking water do not exert cytotoxic effect in splenocytes, nor do they change cellular sensitivity to additional high dose γ-radiation. The latter may be considered as the lack of a radioadaptive response, typically observed after low dose γ-irradiation.
Highlights
Various types of ionizing radiation vary in their potency to induce damage to cells and tissues depending on their linear energy transfer (LET)
That splenocytes belong to, are known for high radiosensitivity, our results indicate that chronic exposure to low doses of β-radiation from HTO in drinking water cause no cytotoxicity in splenocytes
The apoptotic responses we examined develop in the ex vivo context, our previous results had indicated that double strand break responses facilitated by γH2AX in splenocytes are similar between ex vivo and in vivo conditions during first 24 h after the challenging irradiation [11]
Summary
Various types of ionizing radiation vary in their potency to induce damage to cells and tissues depending on their linear energy transfer (LET). There are numerous contributors to such discrepancies; the most significant ones are the use of inappropriate reference radiation types and irradiation modes (acute or chronic) and inappropriately high dose and dose-rates (reviewed in [5]). This ambiguous situation leaves room for public inquiries [6,7], scientific debates [8,9,10], and may stir up unnecessary public concern. This study was designed to evaluate potential cytotoxic effects of tritium given to mice in vivo in the form of HTO in drinking water at very low concentrations. The use of additional challenging high dose γ-irradiation of cells from tritium exposed animals allowed us to evaluate any changes in cellular radiosensitivity that would have otherwise been undetectable
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