NADH required diaphorase or GR to reduce NBT whereas GSH spontaneously reduced NBT within 30 minutes of reaction.

Cell-free assays were used to measure the OD560 of reduced NBT absorbance, for mixtures of 1 mM each NADH and NBT (white boxes) or 1 mM each GSH and NBT (grey boxes) after 30 minutes of reaction without or with enzymes or NEM (median, 25% quartile range (box) and min-max (whiskers), N = 3 to 6 independent assays per condition). Symbols: ** evidence that diaphorase can accept electrons from GSH and inhibit GSH from spontaneously reducing NADH (pvs no diaphorase); *, ***, #, ##: significant differences between selected conditions.