V. An appraisal of indigogenic reactions for esterase localization

Abstract

Results are described of comparative studies of indoxyl acetates, used as indigogenic substrates, in cytochemical staining processes for esterases in formalin-fixed tissues. Correlations have been observed between the staining patterns produced, molecular structures of the substrates and derived dyes, solubilities and substantivities of the dyes, and rates of oxidation of the enzymically produced indoxyls. This has enabled an objective choice to be made of the most precise staining systems, and has led to the systematic development of 5-bromo-4-chloroindoxyl acetate, an improved substrate which enables esterases to be located with a precision of about $0.5\mu $. Kinetics of indoxyl oxidation in tissues indicate that the staining processes have considerable quantitative potentialities.