In vitro synthesis of "amyloid"fibrils from insulin, calcitonin and parathormone.

Insulin, calcitonin and parathyroid hormone subjected to one of two procedures-acidification and heating or incubation with mouse kidney lysosomal extracts-assumed a nonbranching fibrillar structure, 7 to 10 nm in diameter. The preparations showed green birefringence after Congo red staining. The in vitro synthesis from different hormonal polypeptides of fibrils, fulfilling the criteria for the identification of amyloid, indicates that these criteria are related to conformational rather than to compositional properties, and suggests that these hormones may provide the subunit of the amyloid formed in the corresponding endocrine organs.