Mitigative role of melatonin and α-tocopherol against mercury-induced genotoxicity

The present study was conducted to elucidate the protective effect of melatonin (MLT) and alpha-tocopherol on mercury-induced genotoxicity in human blood cultures. The in vitro effects of inorganic mercury added to human lymphocytes on the cell-cycle proliferative index (CCPI)/proliferation replicative index (PRI) and sister chromatid exchange (SCE) using fluorescence plus Giemsa staining were examined. A significant increase occurred in SCE per metaphase (SCE/chromosome and SCE/cell) and inhibition of proliferative kinetics, which resulted in a decline of the replicative index, in comparison to the controls. Treated lymphocyte cultures also exhibited a reduction in %M1 and %M2 metaphase plates, but an increase in %M3 metaphase plates was noticed. Adding alpha-tocopherol and MLT individually and in combination indicated a mitigative effect by reducing the genotoxic potential of treated cultures. The percent amelioration for all the three parameters, namely, frequency of SCE, SCE/plate and SCE/chromosome as well as CCPI, was comparatively high with MLT and alpha-tocopherol in combination than MLT followed by alpha-tocopherol. The percent mitigation was better in combined antioxidant additions to toxicant-exposed cultures, compared to MLT, whereas the percent mitigation by alpha-tocopherol alone was less for average generation time and population doubling time, respectively.