Quantitative evaluation of the trapping reaction of copperthiocholine histochemical procedures for localization of cholinesterases.

The aim of the present study was to investigate whether the trapping reaction of the histochemical procedure for the localization of ChE of Koelle and Friedenwald (1949) and its modification by Brzin and Pucihar (1976) proceeds quantitatively. The weight of the precipitate formed in the tissue sample during the histochemical procedure was compared with enzyme activity of an equal sample. The differential magnetic microbalance was used for measurements of reduced weight and for previous determination of density of the precipitate. The evidence for the composition of the final product was drawn from the quantitative analysis of copper and iodine and from the infrared spectra. Tsuji's statement (1974) that cuprous copper thiocholine iodide is the final product of histochemical procedures investigated was confirmed. It was found that the trapping reaction of the original as well as of the modified procedure under our experimental conditions in tissue sections proceeds quantitatively which means that one of the basic conditions for reliable localization is fulfilled.