Immunohistochemical detection of the enzyme glutamic acid decarboxylase and hormones of the islets of Langerhans in spontaneous insulin-dependent diabetes mellitus in cattle

Immunohistochemical expression of glutamic acid decarboxylase (GAD) enzyme was detected in the pancreatic islets of 12 cattle with spontaneous insulin -dependent diabetes mellitus (IDDM). The most characteristic changes were a trophy and decreased number of pancreatic islets, enlarged islets with vacu olated beta cells, and lymphocytic islet adenitis. Atrophied islets were co mposed of small islet cells without cytoplasmic insulin-positive granules. Immunohistochemically, GAD was not found in the cytoplasm of atrophied isle t cells. Furthermore, enlarged islets consisting of islet cells with vacuol ated cytoplasm were frequently observed. The cytoplasm of vacuolated cells contained very few GAD- and insulin-positive granules, indicating beta cell destruction. Enlarged islets with mild lymphocytic infiltrates were freque ntly observed. These findings suggest that islet cells in cattle with IDDM lose their insulin synthesis function and their ability to regulate hormona l secretion of alpha and delta cells.