Metabolic mapping by enzyme histochemistry in living animals, tissues and cells.

Imaging of reporter molecules such as fluorescent proteins in intact animals, tissues and cells has become an indispensable tool in cell biology. Imaging activity of enzymes, which is called metabolic mapping, provides information on subcellular localisation in combination with functions of the enzymes. The principle of metabolic mapping is imaging of the formation of a reaction product that is fluorescent or coloured by conversion of either a fluorogenic or chromogenic substrate or a fluorescent substrate with different spectral characteristics. Chromogenic and fluorogenic staining methods are discussed here in the context of metabolic mapping in living animals, unfixed cryostat sections of tissues and living cells.