Problems with ultrastructural demonstration of aryl sulphatase activity in rat liver parenchymal cells

The classical method for the electron microscopical demonstration of aryl sulphatase activity in lysosomes (Hopsu-Havu et al. 1967) has been applied for selective demonstration of lysosomes in rat liver parenchymal cells. A positive reaction was obtained in some lysosomes, but the greater part of the precipitate was found in the form of big conglomerates which frequently filled up the interstices between various organelles rather than that they were localized within the organelles. Modifications of the procedure in order to try to confine the demonstration of enzyme activity to lysosomes only included measures: To reduce the amount of primary reaction product, to improve the trapping efficiency of the incubation medium, to prevent possible displacement of the final reaction product. Extralysosomal precipitate persisted under all circumstances; this is interpreted as an artefact rather than as a demonstration of enzyme activity localized in vivo in the cytoplasmic matrix. It is concluded that the present method for demonstration of aryl sulphatase activity is not well suited for microscopical identification of lysosomes in rat liver parenchymal cells.