FELINE INSULAR AMYLOID - ULTRASTRUCTURAL EVIDENCE FOR INTRACELLULAR FORMATION BY NON-ENDOCRINE CELLS

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  • 1 January 1981
    • journal article
    • research article
    • Vol. 45  (2) , 149-156
Abstract
The objective of this ultrastructural study in cats was to investigate the early relationship of pancreatic islet cells with amyloid deposits which are commonly associated with diabetes. Pancreatic islets from 6 domestic cats with minimal and apparently early amyloid were used. Although amyloid deposits were occasionally arranged perpendicularly to .beta. cells, and rarely within deep invaginations of these cells, there was no consistent or convincing relationship of extracellular fibrils to any of the major islet endocrine cell types. Intracellular, membrane-bound, amyloid fibrils were identified in, and restricted to, nongranulated perivascular cells in islets from 2 of the cats. Small and relatively electron-dense amyloid inclusions contained compact arrays of parallel fibrils. Larger inclusions were more electron-lucent and had loosely and randomly arranged fibrils. Indirect evidence strongly suggested that the fibril-laden inclusions resulted from intracellular production rather than from phagocytosis. The definitive identity of these amyloid-containing cell was not determined. These cells lacked secretory granules specific for known islet endocrine cell types and were topographically always located in close proximity to capillaries. The results of the study, therefore, do not directly support a morphologic association of amyloid fibril formation with typical islet endocrine cells. Nonendocrine cells may play a key role in the pathogenesis of insular amyloidosis in the cat.