[Influence of mercury vapors on lymphocytes in vivo and on their susceptibility to UV-C and X-rays, and repair efficiency in vitro].

BACKGROUND

The aim of the study was to compare the levels of DNA and cytogenetic damage in lymphocytes from donors occupationally exposed to mercury vapors and from matched controls as well as their cellular susceptibility to radiation and capabilities to repair DNA damage induced by UV-C or X-ray exposures in vitro.

MATERIALS AND METHODS

To estimate cytogenetic damage, the analysis of sister chromatid exchange frequency (SCE) was used, and to detect DNA damage the alkaline version of single cell gel electrophoresis (SCGE) was applied. To analyze cellular susceptibility, lymphocytes were exposed to 6 J/m2 of UV-C or irradiated with 2 Gy of X-rays. After challenging exposures, cells were incubated for 2 h with or without the presence of cellular mitogen (phytohemagglutinin--PHA).

RESULTS AND CONCLUSIONS

The study did not show statistically significant differences either between the groups, levels of DNA damage (measured as the percentage of cells with comets or comet tail moments), or sister chromatid exchanges. Neither were there significant differences in the levels of DNA damage (measured as tail moment and comet length) detected in UV-C exposed lymphocytes after 2 h incubation in the presence or in the absence of PHA stimulating cells and in the susceptibility to X-ray radiation of lymphocytes between the groups of non-exposed persons and those occupationally exposed to mercury vapors. In the group exposed to mercury vapors, however, statistically significantly higher levels of non-repaired DNA damage measured in X-ray irradiated lymphocytes after 2 h of incubation, with or without the presence of mitogen were observed compared to controls. Significant differences were observed in all types of DNA damage measures (comet tail length, % of DNA, in the comet and comet tail moments). As a result, lymphocytes of donors exposed to mercury vapors showed a statistically lower repair efficiency of X-ray-induced DNA damage both in non-stimulated (70.0% for the exposed, 85.7% for the non-exposed) and stimulated (84.0% for the exposed and 90.4% for the non-exposed) lymphocytes. Cellular DNA repair efficiency decreased with increasing number of years of occupational exposure. Statistically significant DNA repair deficiency in the donors exposed to mercury vapors was also observed when the groups were stratified to smokers and non-smokers.