Effects of malachite green (MG) and its major metabolite, leucomalachite green (LMG), in two human cell lines

Malachite green (MG) is still illegally used as a fungicide in aquaculture. In fish it is absorbed and metabolised to its major reduced metabolite, leucomaiachite green (LMG). This latter represents the main residue found in fish tissues and may persist for several months. Since MG, suspected to act as a tumour promoter in vitro and in vivo, might be also present as a residue in fish, the present study was undertaken to ascertain the in vitro toxicity of both Compounds in two human tumour cell lines (Caco-2 and HEp-2). After 24 h incubation with MG, significant decreases of cell viability, measured by neutral red uptake (NRU) or total protein content (TPC) as well as proliferation capability (colony-forming ability, CFA) were noticed in HEp-2 cells; the mean IC50 value was about 2 mu M. As regards the differentiated Caco-2 cells, MG caused a dose-related significant cytotoxicity, measured either by MTT test, the LDH leakage or NRU, with a mean IC50 value of about 15 mu M. By contrast, LMG disclosed, in both cell lines, a lower cytotoxicity compared to MG. These results also show that HEp-2 cells are more sensitive than intestinal cells to the toxic action of both compounds. (c) 2005 Elsevier Ltd. All rights reserved.