title: Exocytosis of MTT formazan could exacerbate cell injury.
abstract: MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method is one of the most widely used methods to analyze cell proliferation and viability. It is taken up through endocytosis and is reduced by mitochondrial enzymes as well as endosomal/lysosomal compartments, then is transported to cell surfaces to form needle-like MTT formazans; however the effect of MTT itself still remains elusive. Our objective was to investigate the direct effects of MTT on in vitro SH-SY5Y cells. Results showed that the endocytosis of MTT did not cause obvious lesion and induce cell death, but the metabolism and exocytosis of MTT could dramatically damage cells. Our results also indicated that MTT could activate apoptosis related factors such as caspase-8, caspase-3 or accelerate the leakage of cell contents after the appearance of MTT formazan crystals. The present data suggest MTT method should be carefully chosen; otherwise the cell viability would be underestimated and incomparable.
authors.affiliation: Department of Anatomy, Zhongshan School of Medicine, Sun Yat-sen University, Northern Campus, Guangzhou, Guangdong, China.
authors.forename: Lanhai
authors.initials: L
authors.lastname: Lü
authors.forename: Lihong
authors.initials: L
authors.lastname: Zhang
authors.forename: Maria Sen Mun
authors.initials: MS
authors.lastname: Wai
authors.forename: David Tai Wai
authors.initials: DT
authors.lastname: Yew
authors.forename: Jie
authors.initials: J
authors.lastname: Xu
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects*; D005089:Exocytosis; D005562:Formazans / Q000378:metabolism / Q000633:toxicity*; D006801:Humans; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D013778:Tetrazolium Salts / Q000378:metabolism / Q000633:toxicity*
chemical_list: D005562:Formazans; D013778:Tetrazolium Salts; C079782:MTT formazan; D053148:Caspase 3