Senile cardiac amyloid: evidence that fibrils contain a protein immunologically related to prealbumin.

Antiserum specific for human prealbumin (HPA) was studied by indirect immunofluorescence on tissue sections of cardiac ventricles containing senile cardiac amyloid. The pattern of reactivity was identical to that previously reported for an antiserum specific for protein ASc1 (formerly designated ASCA present in these tissues. Anti-HPA failed to react with isolated atrial amyloid (IAA), primary amyloid (A lambda I, A lambda IV, A lambda VI), secondary amyloid (AA), amyloid associated with medullary carcinoma of the thyroid (AEt), pancreatic amyloid associated with adult onset diabetes, cerebral amyloid present in Alzheimer's disease or lichen amyloid. THe reaction of anti-HPA was completely blocked by purified human prealbumin but was not influenced by absorption with purified human albumin or proteins extracted from any amyloid types tested. The anti-HPA reaction was also completely blocked by purified protein ASc1, and the reaction of anti-ASc1 was similarly blocked by purified HPA. These studies suggest that senile cardiac amyloid of the ASc1 type contains prealbumin or a protein antigenically closely related to this molecule.