Localization of monoamine oxidase A and B in human pancreas, thyroid, and adrenal glands

We studied monoamine oxidase (MAO) A and B localization in human pancreas, thyroid gland, and adrenal gland by immunohistochemistry. The primary antib odies used were mouse monoclonal anti-human MAO-A (6G11/E1) and anti-human MAO-B (3F12/G10/2E3). Samples were obtained from six routine autopsy cases and fixed in 2% paraformaldehyde. Exocrine pancreas showed a widespread dis tribution of MAO-A, whereas MAO-B was present only in centroacinar cells an d epithelial cells of pancreatic ducts. In endocrine pancreas, MAO-A was ob served in around 50% of islet cells, whereas MAO-B was less abundant and wa s restricted to the periphery of islets. Thyroid gland showed strong MAO-A immunoreactivity in all cell types and was MAO-B-negative. In adrenal gland , the capsule displayed MAO-A but not MAO-B immunoreactivity, whereas the c ortex showed widespread MAO-A staining but was MAO-B-negative in interstiti al cells. Finally, in the medulla only a few scattered cells showed either MAO-A or MAO-B immunoreactivity. To our knowledge, these data represent the first study of the cellular distribution of MAO-A and MAO-B in the three h uman tissues included.