Marshall N J, Goodwin C J, Holt S J
Department of Molecular Pathology, University College London Medical School, UK.
Growth Regul. 1995 Jun;5(2):69-84.
Microculture tetrazolium assays (MTAs) are being widely applied to probe the relationships between cell survival, growth, and differentiation and also to investigate associations between compromised cell metabolism, oxidative stress, and programmed cell death as occurs in apoptosis. MTAs rely upon the cellular reduction of tetrazolium salts to their intensely coloured formazans. The resulting colorimetric assays form the basis of exceptionally precise systems which are technically amenable and capable of a high throughput of samples. As a consequence, MTAs are being used to monitor responses to both extracellular activators and toxic agents in disciplines as diverse as radiobiology and endocrinology. We review the chemistry and histochemical applications of tetrazolium salts and subsequently discuss the criteria for their use in MTAs. These assays are one of the latest examples of the application of the tetrazolium/formazan system to cell biology. We outline current views on the mechanisms of the bioreduction of tetrazolium salts. These probably combine to reflect the integrated pyridine nucleotide dependent redox state of the cell. We try to illustrate how an understanding of these mechanisms helps to avoid some of the pitfalls of the MTA systems. There is now for example, extensive evidence that changes in cell culture environments, such as glucose supply or pH of the medium, influence the reduction of tetrazolium salts and thereby introduce artefacts into MTAs. Finally, we provide examples of situations in which MTAs can be used to complement other more established experimental systems. They then act as unique probes with which to investigate changes in the redox state of the cell. These changes are associated with regulation of cell growth, proliferation and differentiation and conversely, the different pathways leading to cell death.
微量培养四氮唑试验（MTAs）正被广泛应用于探究细胞存活、生长和分化之间的关系，以及研究细胞代谢受损、氧化应激与凋亡中发生的程序性细胞死亡之间的关联。MTAs依赖于细胞将四氮唑盐还原为颜色强烈的甲臜。由此产生的比色测定法构成了极其精确系统的基础，这些系统在技术上易于操作且能够高通量处理样本。因此，MTAs正被用于监测放射生物学和内分泌学等不同学科中细胞对细胞外激活剂和有毒物质的反应。我们回顾了四氮唑盐的化学性质和组织化学应用，随后讨论了其在MTAs中使用的标准。这些试验是四氮唑/甲臜系统应用于细胞生物学的最新实例之一。我们概述了目前关于四氮唑盐生物还原机制的观点。这些机制可能共同反映了细胞中依赖吡啶核苷酸的综合氧化还原状态。我们试图说明对这些机制的理解如何有助于避免MTA系统的一些陷阱。例如，现在有大量证据表明，细胞培养环境的变化，如葡萄糖供应或培养基pH值，会影响四氮唑盐的还原，从而在MTAs中引入假象。最后，我们提供了一些情况的例子，其中MTAs可用于补充其他更成熟的实验系统。然后，它们作为独特的探针，用于研究细胞氧化还原状态的变化。这些变化与细胞生长、增殖和分化的调节相关，反之，与导致细胞死亡的不同途径相关。
