DETERMINATION OF MELAMINE CYTOTOXICITY

Cytotoxic potential of melamine was evaluated with the use of two in vitro models i.e. cell cultures of rat hepatoma (line FaO) and rat skeletal muscle (line L6). The cultures were exposed for 24, 48, and 72 h to melamine at eight concentrations, ranged from 0.01 to 10 mM. Four different assays were applied in which various biochemical endpoints were assessed: mitochondrial activity - MTT reduction assay, proliferation - Commassie Brilliant Blue (CBB) dye binding assay, lysosomal activity - neutral red uptake (NRU) assay, and membrane integrity - LDH release assay. Effective concentrations (EC20, EC50 , EC80) were calculated from concentration-response curves, and then they were averaged over three independently conducted experiments. It was found that MTT assay was the most sensitive to this compound. After 48 h exposure EC50 values (mM, mean ± SD) for FaO and L6 cells were 6.4 ± 0.62, and 8.2 ± 1.51, respectively. The inhibition of lysosomal activity measured by NRU assay, and damage of plasma membrane measured by LDH assay were detected in L6 (but not in FaO) cells; however, the effects took place after longer (72 h) exposure. At that time EC50 values were 5.2 mM and 9.2 mM for NRU and LDH, respectively. In spite of the low cytotoxicity of melamine, more studies are needed for hazard identification and characterization of the compound.