The phosphorus content of lysosomes in hepatocytes and Kupffer cells. A study using electron-spectroscopic imaging

In the present study, the distribution of phosphorus was analyzed within lysosomes of hepatocytes, Kupffer cells and mast cells in untreated liver tissue of mice by the use of electron-spectroscopic imaging, a new electron-microscopical method which combines microanalysis with ultrastructural representation and allows to image the spatial distribution of light elements such as O, N or P in cells and tissues. The obtained analytical data unfolded marked differences regarding the phosphorus content of lysosomes within hepatocytes. Whereas peribiliary bodies always included phosphorus highly condensed in a coarse-granular distribution, the lysosomes apart from biliary capillaries contained different amounts of phosphorus, varying from high concentration to moderate and negligible amounts appearing as dust-like powder in the lysosomal interior. In contrast, the lysosomes of Kupffer cells always comprised phosphorus in high density and similar concentration as it is found in cytoplasmic ribosomes. These results confirm a pronounced and unexpected heterogeneity regarding the elemental composition of lysosomes in hepatocytes and Kupffer cells. It may be assumed that this heterogeneity is not accidental but based on differences in the functional state of lysosomes and the activity of their hydrolytic enzymes.