Fatty acid composition of muscle tissue measured in amphibians living in radiologically contaminated and non-contaminated environments.

Fatty acid composition was identified as a potential biological indicator of the effects of environmental exposure to radiological contaminants. This end point was measured in muscle tissues of Mink frogs ( Rana septentrionalis ) obtained from a radiologically contaminated pond and from a non-contaminated pond. It was also measured after the frogs obtained from both ponds were exposed to a 4 Gy (60)Co γ radiation dose delivered in vivo at a dose rate of approximately 8 Gy/min. Statistically significant differences for the increase of a couple of polyunsaturated omega-3 fatty acid residues and the decrease of a polyunsaturated omega-6 fatty acid residue were observed between radiologically contaminated and non-contaminated frogs, indicating a partial remodeling of muscle lipids in response to a chronic low-dose tritium exposure. The effects of an acute high-dose exposure to (60)Co γ radiation, either for the radiologically contaminated or non-contaminated frogs indicated fast post-irradiation fatty acid changes with an increase of polyunsaturated and decrease of saturated fatty acid contents. Fatty acid composition was found to be a sensitive marker that may be useful to study and monitor biota health in environments that are radiologically contaminated, as well as for understanding the differences between low chronic and high acute stress responses.

Adaptive response in frogs chronically exposed to low doses of ionizing radiation in the environment.

Using the micronucleus assay, decreased levels of DNA damage were found after high dose ionizing radiation exposure of liver cells taken from frogs inhabiting a natural environment with above-background levels of ionizing radiation, compared to cells taken from frogs inhabiting background areas. The data obtained from a small number of animals suggest that stress present in the above-background environment could induce an adaptive response to ionizing radiation. This study did not reveal harmful effects of exposure to low levels of radioactivity. On the contrary, stress present in the above-background area may serve to enhance cellular defense mechanisms.