Morphologic demonstration of cytoplasmic ASSAM-related antigenic substance (CASSAM) by an immunoperoxidase technique.

Murine senile amyloid protein identified in the senescence-accelerated mouse (SAM) was called ASSAM, and the ASSAM-related antigenic substance was detected in the cytoplasm of hepatocytes, columnar epithelia of the small intestine, and epithelia of the proximal convoluted tubules of the kidney, with the use of an immunoperoxidase method. This substance, called CASSAM (cytoplasmic ASSAM-related antigenic substance), did not stain positively with Congo red nor fibril structure, as determined under an electron microscope. As the ASSAM (senile amyloid) deposition increased with advancing age, CASSAM observed in hepatocytes and columnar epithelia decreased both in SAM-P and SAM-R strains. In the liver of the SAM-P strain in particular, the incidence and intensity in deposition of ASSAM increased rapidly from 5 months of age; on the other hand, CASSAM observed in the hepatocytes decreased rapidly at about the same time. Cycloheximide-treated animals showed a significantly low concentration of SASSAM (serum ASSAM-related antigenic substance) and also a low incidence and intensity of CASSAM observed in the cytoplasm of the hepatocytes and epithelia of the small intestine. In colchicine-treated animals, SASSAM concentration was slightly lower, and the severity of CASSAM observed in the cytoplasm was slightly higher, in the liver and kidney, as compared with control values. CASSAM is assumed to be synthesized in the cytoplasm of the cell and to be secreted alone or in the lipoprotein form into the serum. This CASSAM or lipoprotein including CASSAM is perhaps a constituent of SASSAM (CASSAM is assumed to include apoSASSAM) and the hepatocytes and intestinal mucosal epithelia are possible production sites of apoSASSAM.