The perisinusoidal functional unit in amyloidosis

Summary The close morphological and functional relations between the various components of the perisinusoidal functional unit may be demonstrated by combination of ultrastructural results with the latest findings in the context of intra-hepatic synthesis and transformation of amyloid. The precursors af amyloid, synthesised in hepatocytes in the region of the endoplasmic reticulum, lysosomes, and plasma membrane of the vascular pole, are moved into the vascular system together with high-density lipoproteins which are probably identical with lipoprotein vesicles close to plasma membranes and in Disse space, and in the vascular system they are transformed to Serum Amyloid A (SAA). A certain role is probably played by Kupffer cells in polymerisation of amyloid A to fibrils. Growing accumulation of fibrils causes ligature and melt-off of peripheral parts from the vascular pole of hepatocytes, with its volume being substantively reduced, so that the spacing between plasma membrane and nucleus may reduce from something between 10 and 12 μ m to below 1 μ m. There is neither any compression of cytoplasm nor translocation of organelles. Hence, the process can be interpreted as a specific form of atrophy.