Morphological and histochemical characteristics of pigments in aging F344 rats

Pigments found in spleen, lymph nodes, kidney, thyroid, adrenal, liver, ovary, central nervous system, heart and connective tissues of aging F344 rats were studied morphologically and histochemically. The morphology of the pigment accumulations depended on the tissue affected. Pigments resembling lipofuscin were found in most of these tissues. The ultrastructural appearance of siderosomes in splenic macrophages suggested that erythrocyte degradation was responsible for pigment production. Adrenal ultrastructure showed that lipofuscin-like material may have originated from degradation of lipid droplets of epithelial cells.