Cytochemical demonstration of guanase in human liver using yellow tetrazolium

Abstract

We reported a modified procedure for histochemical demonstration of guanase in human tissues involving hydrolytic deamination of the substrate guanine to xanthine via guanase, and then oxidation of xanthine to uric acid, with concomitant reduction of nitro tetrazolium blue (NBT). In this report, we describe a modification of this method for cytochemical demonstration of guanase at the fine structural level using yellow tetrazolium in place of NBT for determination of the intracellular distribution of guanase in human hepatocytes.
In the hepatocytes, the reaction products were seen to be concentrated in the nucleus, in mitochondria, cisternae of the smooth and/or rough-surfaced endoplasmic reticulum and lysosomes. The precise locations of the reaction product in the cisternae of the nuclear envelope, chromosomes and nucleus could not be determined. However, the reaction products in the mitochondria were clearly seen to be located in the spaces of cristae.
This information of the intracellular distribution of guanase in normal hepatocytes will be useful in determing the physiological role of this enzyme and in further studies on diseased hepatocytes including those in non-A non-B hepatitis.