MTT

MTT (3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) is a reagent used in the measurement of in vitro cell proliferation.

Tetrazolium salts have been the most widely used tools in cell biology for deternining the metabolic activity of cells ranging from microbial origin to mammalian. Fractionation studies in mammalian cells indicate that NADH, the reduced pyridine nucleotide cofactor, is responsible for most MTT reduction, which is further supported by studies with whole cells.

In vitro: It has been found that MTT reduction was associated not only with mitochondria, but also with the cytoplasm and nonmitochondrial membranes including endosome/lysosome compartment and plasma membrane. The net positive charge on MTT appears to be the predominant factor involved in their cellular uptake through the potential of plasma membrane. However, the second generation tetrazolium dyes (XTT, WST-1 and to some extent, MTS) that form water-soluble formazans and require an intermediate electron acceptor for reduction, are characterised by a net negative charge and therefore are largely cell-impermeable [1].

In vivo: MTT currently is only used for in vitro cell proliferation determination and there is no in vivo study reported.

MTT (3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) 是一种用于检测体外细胞增殖的试剂。

四唑盐一直是细胞生物学中使用最广泛的工具，用于确定从微生物来源到哺乳动物细胞的代谢活动。哺乳动物细胞中的分离研究表明，还原的吡啶核苷酸辅助因子 NADH 是大多数 MTT 减少的原因，这进一步得到了全细胞研究的支持。

体外:已发现 MTT 降低不仅与线粒体有关，而且与细胞质和非线粒体膜（包括核内体/溶酶体区室和质膜）有关。 MTT 上的净正电荷似乎是通过质膜电位参与细胞摄取的主要因素。然而，形成水溶性甲臜并需要中间电子受体进行还原的第二代四唑染料（XTT、WST-1，在某种程度上还有 MTS）具有净负电荷的特点，因此在很大程度上是细胞不可渗透的 [ 1].

体内:MTT目前仅用于体外细胞增殖测定，尚无体内研究报道。

Reference:
[1] Berridge MV,Herst PM,Tan AS.  Tetrazolium dyes as tools in cell biology: new insights into their cellular reduction. Biotechnol Annu Rev.2005;11:127-52.