The ultrastructural localization of sulfated proteoglycans is identical in the amyloids of Alzheimer's disease and AA, AL, senile cardiac and medullary carcinoma-associated amyloidosis.

The cationic dyes cuprolinic blue and ruthenium red were used to ultrastructurally localize proteoglycans (PGs) within the neuritic plaque and neurofibrillary tangle of Alzheimer's disease. Highly sulfated PGs were specifically localized to the amyloid fibril of the neuritic plaque and the paired filaments of the neurofibrillary tangle. This demonstrates that highly sulfated PGs either comprise part of the Alzheimer's amyloid fibril and paired filament or are intimately associated with them. Four unrelated types of amyloid--AA (inflammation-associated), AL (immunoglobulin light chain), senile cardiac (prealbumin) and medullary carcinoma-associated amyloid (procalcitonin)--showed an identical pattern of localization of highly sulfated PG to the different amyloid fibrils. This constant close spatial relationship between PGs and diverse amyloid proteins suggests that PGs may play a role in amyloidogenesis.