Selective Binding of Fluoresceinated-Avidin to A-Cells of Sectioned Pancreas

Fluoresceinated-avidin (FITC-avidin) was observed to bind specifically to a subset of pancreatic islet cells in sections of both human and rat pancreas. FITC-avidin binding was inhibited by excess unlabeled avidin, and by biotin, but not by glucagon, somatostatin, or insulin. Labeling of islets with anti-insulin, anti-glucagon, anti-somatostatin, and anti-human pancreatic polypeptide antibodies showed the avidin binding subset to correspond to islet cells identified by anti-glucagon antibody. Conversely, avidin reacted with no insulin, somatostatin, or cells containing HPP. We conclude that avidin localizes specifically to A-islet cells. Binding may be to a biotin-containing enzyme within the A-cells, but the precise molecular site of binding is currently unidentified.