Ultrastructural studies of renal peritubular amyloid experimentally induced in guinea pigs: III. Blood and Lymphatic Capillaries

Abstract

The fine structure of renal peritubular blood and lymphatic capillaries was studied in amyloidotic and control guinea pigs. The majority of peritubular blood capillaries possessed a “fenestrated endothelium,” but “continuous capillaries” were also occasionally found in this area. Lymphatic capillaries had a “continuous endothelium” but “discontinuous basement membrane,” and were associated with “lymphatic anchoring filaments” as usual. The frequency of amyloid deposits was comparable in both the blood (either fenestrated or continuous) and lymphatic capillaries. The approximation of the amyloid deposits to the cells and the seemingly intimate ultrastructural relationship between cells and the tufts of well-oriented amyloid fibrils suggested that the capillary endothelial cells and even more particularly the pericytes might contribute to the formation of amyloid fibrils. In addition, the ultrastructural similarities and differences that exist amongst amyloid fibrils, lymphatic anchoring filaments, and a variety of connective tissue microfibrils were discussed.