CELLULAR TOXICITY OF MALACHITE GREEN AND LEUCOMALACHITE GREEN EVALUATED ON TWO RAT CELL LINES BY MTT, NRU, LDH, AND PROTEIN ASSAYS

The cytotoxicity of malachite green (MG) and its major metabolite, leucomalachite green (LMG) was investigated using rat FaO and L6 cell lines. Eight concentrations ranging from 0.1 to 100 µM (MG) and 10 to 1,000 µM (LMG) were tested in three independent experiments. Four cytotoxicity assays were applied in which various biochemical endpoints were assessed: mitochondrial activity (MTT assay), proliferation (total protein content assay), lysosomal activity (neutral red uptake assay), and membrane integrity (LDH leakage assay). The mean effective concentrations (EC50) were calculated from the dose-response curves after 24, 48, and 72 h of exposure. The concentration- and time- dependent effects were observed. MG was very toxic and FaO cells were more sensitive than L6 cells. EC50 values were <10 µM in MTT, NRU, LDH tests (in FaO cells), and in NRU, MTT (in L6 cells) indicating that the primary mechanism of toxicity is inhibition of mitochondrial and lysosomal activity. The LMG gave only slight toxic effect at the hundreds times higher concentrations, with the exception of NRU assay for which EC50 values after 48 and 72 h exposure were very low (<10 µM).