[Methyltetrazolium bromide (MTT) was applied for bioassay of environmental radioactivity in vivo]

The MTT-assay is a colorimetric assay that measures the activity of enzymes that reduce MTT (a yellow tetrazolium bromide) in living cells. The MTT-test has been traditionally applied for the analysis of drug cytotoxicity in vitro. In our study MTT-assay was first applied for the investigation in vivo of the mechanisms of non-targeted effects of radiation and development of stress in multicellular crustaceans Daphnia magna. MTT test was based on the analysis of variation in the optical density of the irradiated Daphnia, which is proportional to the amount of formazan formed as a result of restoring MT with the help of dehydrogenases. So this indicator measures the effectiveness of the toxic effect of gamma-radiation. It describes the change in the balance of normal and damaged cells, suppression of the total dehydrogenase activity and other factors that are responsible for the metabolism of a multicellular organism. Daphnia were exposed to acute 60Co gamma-rays. According to our data, the effectiveness of toxicity was significantly raised in the two groups exposed to 100 and 1000 mGy of gamma-rays. Given the results of in vitro studies, our data therefore indicate that the compromised viability of irradiated Daphnia may be attributed to the cytotoxic effects within the dose-range of 100 and 1000 mGy. The results obtained in this study show that Daphnia represent a very useful experimental model, which allows a very efficient and quick analysis of many aspects of non-targeted effects of ionising radiation.