Amyloid deposition in the digestive tract in casein-induced experimental amyloidosis in mice.

In mice with casein-induced experimental amyloidosis, the incidence of amyloidosis in various organs was examined in relation to time, and the extent of amyloid deposition in the digestive tract was investigated. Amyloid was deposited first in the spleen, a little later in the digestive tract, and then in the liver and kidney. In the digestive tract, amyloid appeared simultaneously in the small and large intestine, and later in the glandular stomach. Amyloid deposition was most severe in the ileum, while it was not induced in the esophagus or non-glandular stomach. Initially, amyloid deposition was observed along the small blood vessels and/or epithelial basement membranes in the lamina propria mucosa (LPM); it then extended to the stroma in the LPM. Amyloid deposition in each portion of the digestive tract had characteristic patterns in the LPM. Deposition of amyloid fibrils was confirmed by electron microscopy. The results suggest that the gastrointestinal biopsy used widely to diagnose human reactive amyloidosis is a sensitive early indicator of amyloidosis.