Objectives: The aim of this study was to investigate the radioprotective effect of green tea against genotoxicity induced by gamma irradiation in cultured blood lymphocytes from 5 human volunteers. Materials and Methods: Peripheral blood samples were collected from volunteers before and 1, 3 and 5 h after once drinking of 4 gr green tea in 280 ml boiling water and at 1 h post 5 constitutive days drinking of green tea with the same quantity. At each time point, the whole blood samples were exposed to 200 cGy of 60 Co gamma irradiation and then cultured with mitogenic stimulation to determine the chromosomal aberration in micronucleus assay on cytokinesis-blocked binucleated cells. Results: For each volunteer, as was expected, the results showed a significant increase in the incidence of micronuclei after exposure of cells to gamma irradiation as compared to Non-irradiated control samples. Only blood sample lymphocytes collected 3 h after once drinking of green tea exhibited a significant decrease in incidence of micronuclei compared to not treated with green tea irradiated samples. Conclusion: This result suggests the radioprotective ability of green tea at specified time after drinking against ionizing radiation in human lymphocytes.

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