Gamma ray induced genetic changes in different organs of chick embryo using peripheral blood micronucleus test and comet assay.

Ionizing radiation is known to produce a variety of cellular and sub cellular damage in both prokaryotic and eukaryotic cells. Present studies were undertaken to assess gamma ray induced DNA damage in different organs of the chick embryo using alkaline comet assay and peripheral blood micronucleus test. Further the suitability of chick embryo, as an alternative model for genotoxicity evaluation of environmental agents was assessed. Fertilized eggs of Rhode island red strain were exposed to 0.5, 1 and 2Gy of gamma rays delivered at a dose rate of 0.316Gy/min using a (60)Co teletherapy machine. Peripheral blood smears were prepared from 8- to 11-day-old chick embryos for micronucleus test. Alkaline comet assay was performed on 11-day-old chick embryos in different organs such as the heart, liver, lung, blood, bone marrow, brain and kidney. Analysis of the data revealed a significant increase in the frequency of micronucleated polychromatic erythrocytes, micronucleated normochromatic erythrocytes and total micronucleated erythrocytes in the peripheral blood of gamma irradiated chick embryos at all the doses tested as compared to the respective controls. The polychromatic to normochromatic erythrocytes ratio which is an indicator of proliferation rate of hematopoetic tissue, decreased in the irradiated groups as compared to the controls. Data obtained from comet assay, clearly demonstrated a significant increase in DNA strand breaks in all the organs of irradiated chick embryos as compared to the respective controls. However, maximum damage was observed in the heart tissue on all the doses tested, followed by kidney, brain, lung, blood and liver. The lowest damage was observed in the bone marrow tissue. Both micronucleus test and comet assay were found to be suitable biomarkers for the evaluation of genotoxicity of gamma radiation in the chick embryo.