Analysis of cellular effects by continuous exposure AT low concentration of tritium.

This study focused on the induction of DNA double-strand breaks (DSBs) in hTERT-immortalized normal human retinal pigment epithelial cells (RPE1-hTERT) continuously exposed to tritiated water (HTO) and organically bound tritium (OBT) at 6000 Bq/ml. The results showed that OBT, specifically tritium-labeled thymidine (^3H-Thy) and palmitic acid (^3H-PA), induced more DSBs than HTO, with ^3H-Thy causing the highest level of damage. Importantly, the extent of DSB induction correlated not with the total intracellular tritium amount but with its subcellular localization, particularly the amount localized in the insoluble nuclear fraction associated with DNA. The study suggests that both intracellular concentration and subcellular distribution of tritium should be considered in evaluating its biological impact, especially regarding radiation-induced DNA damage.