Template_CLM_10LM1 Micronuclei and nuclear abnormalities in fish as biomarkers of cytotoxicity and genotoxicity of gamma radiation, chromium 51, in an aquatic environment

Toxic effects of gamma radiation on fish, as biomarkers

Abstract

Ionizing radiation is a genotoxic agent, inducing gene mutations and cellular death and accidents or nuclear disasters can contaminate water bodies and environmental monitoring methods are needed to assess low levels of radiation. The micronucleus and test has stood out as a biomarker of DNA damage and fish such as Nile tilapia can be an excellent model to assess damage caused by physical and chemical agents, due to their biological and environmental characteristics. The objective of this study was to evaluate the genotoxicity in fish, under to radioactive chromium exposure (⁵¹Cr), gamma radiation, utilizing Micronuclei Test (MNs) and nuclear abnormalities (NA). In the present study, freshwater fish, Oreochromis niloticus, Nile tilapia, were subjected to daily gamma radiation of 20 Gy, through the incorporation of ⁵¹Cr₂O₃ in the diet, administered during the seven days of the experimental period, totaling approximately 140 Gy. Peripheral blood samples were collected at different moments [days 0 (control), 1, 2, 3, 4, 5, 6, 7] and analyzed using the erythrocyte micronucleus assay. The results indicated that Nile tilapia showed to be sensitive to gamma radiation. The nuclear anomalies observed were micronuclei (MN), deformed nucleus (DN), nuclear bud (NBu), nuclear bridge (NBr), binucleated cells (BNC) and apoptotic cells (AC). ⁵¹Cr exposure caused a statistically significant increase (p<0.05) in nuclear abnormalities after subchronic exposure to radionuclide, indicating a time-dependent effect, which correlated positively with micronuclei and other nuclear abnormalities. Nuclear abnormalities were resultants of gamma radiation induced genotoxicity due to the decay of the radionuclide, administered orally. The results suggest that morphological analysis and the frequency of micronuclei in haemocytes of Nile tilapia can be considered reliable parameters in assessing the genotoxic action in aquatic environments.