Systemic senile amyloid in senescence-accelerated mice. A unique fibril protein demonstrated in tissues from various organs by the unlabeled immunoperoxidase method.

Tissue sections of senescence-accelerated mice (SAM) and of mice with normal aging characteristics (R series) were studied using a peroxidase-antiperoxidase (PAP) method with specific antisera against a unique amyloid fibril protein (AS/SAM) and against murine protein AA. Anti-AS/SAM antisera reacted with amyloid tissues of SAM and aged R series mice but not with normal tissues or amyloid tissues containing protein AA. Reactivity of this and serum could be abrogated by absorption with purified AS/SAM. Amyloid deposits in liver, kidney, spleen, gastrointestinal tract, lung, heart, gonads, pancreas, salivary glands, adrenal, thyroid, skin epineurium, and blood vessels were positive for AS/SAM in both the SAM and R series. Brain and bone medulla, however, were not stained. The amyloid deposited in gonads, papillary layer of dermis, and epineurium was exclusively AS/SAM. The amyloid observed in most of the P-1 series mice was AS/SAM. In the P-2 series and R series, protein AA frequently coexisted with AS/SAM as demonstrated using a double staining method. Each amyloid localized preferentially in the liver, spleen, and gastrointestinal tract.