Cj. Goodwin et al., GROWTH HORMONE-RESPONSIVE DT-DIAPHORASE-MEDIATED BIOREDUCTION OF TETRAZOLIUM SALTS, Biochemical and biophysical research communications, 226(3), 1996, pp. 935-941
Microculture tetrazolium assays (MTAs) rely upon the bioreduction of t
etrazolium salts to their intensely coloured formazans. Although these
assays are being extensively used, the intracellular mechanisms respo
nsible for the formazan production are not known. MTAs currently provi
de the basis for uniquely precise in vitro bioassays for human growth
hormone (hGH) which use the Nb2 cells. We have compared two contrastin
g tetrazolium salts, namely 4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltet
razolium bromide (MTT) and henyl)-2-(4,5-dimethylthiazolyl)-3-(4-sulfo
phenyl) tetrazolium, inner salt (MTS), in this system. An intermediate
electron acceptor (IEA) is obligatory for the MTS- but not the MTT-bi
oassay. We report that inhibitors of DT-diaphorase abolished MTS- but
not MTT-formazan production. We conclude that substitution of MTT with
MTS/menadione resulted in formazan production via a different electro
n transfer pathway which is exclusively mediated by DT-diaphorase. (C)
1996 Academic Press, Inc.