Application of MTT-assay to estimate long-term effects of acute G-radiation on Daphnia magna

We investigated applicability of MTT-assay for study of cytotoxic effects of low-level g-radiation on multicellular crustacean D. magna. The species represent a very useful model for quick analysis of long-term cytotoxic effect of different agents including antitumor pharmaceuticals. The life span of D. magna is relatively short and seldom exceeds 10-11 weeks; they are also characterized by quite short duration of embryonic and postembryonic development, 3-4 days, and gestation of 5-8 days. At present, fast-growing application of radiopharmaceuticals (RFP) for diagnosis and treatment requires research into cytotoxicity and radiotoxicity of RFPs and products of their biotransformation in a body. Currently for preclinical study of radiopharmaceuticals mice and rats are used in bio-pharmacology. However, simple and express tests providing new insights into the mechanisms underlying the efficiency and toxicity of RFP are required. Over recent years we have studied long-term effects of low-dose radiation using D. magna as model for analysis of long-term effects of low-level g-radiation and MTT-assay for assessment of the effects on metabolic activity in the species. In the article we present results of research on effects of low-level g-radiation (10, 100 and 1000 mGy) on D. magna Straus and its non-irradiated offspring of the first generation. To assess cells metabolism in irradiated D. magna MTT-assay was used. The assay is based on the property of NAD(P)H-dependent oxidoreductase enzymes, contained in metabolically active cells, to reduce yellow tetrazolium salt (MTT) to the insoluble deep purple formazan. After dissolution of formazan crystals absorbance of the solution was measured. In our study we found that MTT-assay can be used for assessment of radiotoxic effects from exposure of D. magna to low-level g-radiation; the toxic effect was passed to non-exposed offspring of the first generation; the toxic effect is low after exposure to 10 mGy. Our data also demonstrate that D. magna is a sensitive model that can be used for express analysis of long-term effects of low-level radiation.