WST-1 Reduction at the RBC Plasma Membrane

Tetrazolium dyes have often been used as electron acceptors in measurements of cell proliferation rates (Berridge and Tan, 1993; Ishiyama, et al., 1993; Berridge, et al., 1996), in histochemical procedures (Zamudio, et al., 1969; May, et al., 1995b; Demehin, et al., 2001), and for assaying redox enzymes (Berridge and Tan, 1993; Mittler and Zilinskas, 1993; Debnam and Shearer, 1997; Ye, et al., 1997; Berridge and Tan, 1998, 2000a, 2000b; Ukeda, et al., 1999; Peskin and Winterbourn, 2000; Tan and Berridge, 2000; Demehin, et al., 2001; Baker, et al., 2004a). On reduction, tetrazolium salts produce a highly coloured end-product called formazan. In general, tetrazolium salts are soluble due to the cationic character of their heterocyclic ring, whereas the formazan products are electrically neutral and insoluble in water (Ishiyama, et al., 1993). The development of tetrazolium salts that are reduced to water soluble formazans (Ishiyama, et al., 1993) has broadened the appeal of these redox dyes.