一种新的四唑类化合物3-(4,5-二甲基噻唑-2-基)-5-(3-羧甲氧基苯基)-2-(4-磺基苯基)-2H-四唑内盐(MTS)，在细胞培养试验中作为替代MTT的试剂，加入酚噻嗪甲磺酸盐(PMS)后生成水溶性福马唑产物，其波长最大吸收在490-500nm磷酸盐缓冲液中可测得。产生的有色产物数量与细胞数量以及细胞与MTS/PMS的孵育时间成正比。MTS/PMS在所有测试的细胞系中都有反应，包括鼠白血病L1210细胞、鼠艾氏肿瘤细胞、鼠3T3成纤维细胞和人类结肠癌细胞(HT-29)。HT-29和3T3成纤维细胞比减少MTT更高效地减少MTS/PMS。与MTT产生的产物数量相当，MTS/PMS产生的产物优异。用MTS/PMS获得的嘧唑咪唑并唑的IC50值为200微米，5-氟-2'-脱氧尿苷的IC50值为0.9纳米。这些值与直接细胞计数获得的IC50值相比非常有利。此外，在不同孵育时间下，在96孔板中测定福马唑产物的吸收度也能得到相同的IC50值。

A new tetrazolium analog of 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) was evaluated as a substitute for MTT in the microculture screening assay for in vitro cell growth. This new tetrazolium compound, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2- (4-sulfophenyl)-2H-tetrazolium, inner salt (MTS), in the presence of phenazine methosulfate (PMS), gave a water-soluble formazan product that had an absorbance maximum at 490-500 nm in phosphate-buffered saline. The amount of colored product formed was proportional to the number of cells and the time of incubation of the cells with MTS/PMS. MTS/PMS was reactive in all the cell lines tested which included mouse leukemia L1210 cells, mouse Ehrlich tumor cells, mouse 3T3 fibroblasts, and human colon tumor cells (HT-29). HT-29 and 3T3 fibroblasts reduced MTS/PMS more efficiently than they reduced MTT. Comparable to the amount of product formed from MTT, MTS/PMS gave excellent product formation. The IC50 value for pyrazoloimidazole obtained using MTS/PMS was 200 microM; for 5-fluoro-2'-deoxyuridine, the IC50 value was 0.9 nM. These values compared very favorably with the IC50 values obtained by direct cell counts. Further, the same IC50 values were obtained when the absorbances of the formazan product in the 96-well plates were determined after different times of incubation.