Effects of NAC on Fish Hepatoma Cells Treated with Ionizing Radiation and Mercury Chloride

Organisms are exposed to natural radiations from cosmic or terrestrial origins. Radiation is known to cause cell death, mainly due to its ability to produce reactive oxygen species in cells. The combined action of ionizing radiation with various chemicals is an inevitable feature of modern life. N-acetyl-L-cysteine (NAC) is a well-known sulfhydryl-containing antioxidant whose role in radioprotection has been explored in several studies. The present study was designed not only to assess the synergistic effects between radiation and HgCl2, but also to investigate the protective effects of NAC on cells. Simultaneous treatment of the cells with ionizing radiation and HgCl2 resulted in a dramatic increase of cell death, while neither of them showed cytotoxic effects when treated alone. The cytotoxicity of ionizing radiation was enhanced in the presence of HgCl2. An analysis of the extent of synergistic interaction allows to make quantitative estimation of irreversibly damaged cells after the combined exposure. NAC in lower concentrations prevented cell death after irradiation with lower doses (<300 Gy). However it did not prevent cells from radiation-induced death after irradiation with higher doses (300, 500 Gy). The intracellular GSH levels significantly decreased after treatment with radiation alone while the combined treatment of NAC and radiation alleviated the decrease in GSH levels. The investigations give a clue for the establishment of fundamental theories associated with positive efficacy of radiation applications including synergistic or protective effects. This study may be also useful for elucidating the effects of radiation on aquatic organisms.