IMMUNOHISTOCHEMICAL IDENTIFICATION OF ADRENOMEDULLIN IN HUMAN, RAT, AND PORCINE TISSUE

The histological localization was investigated of adrenomedullin (AM), a novel vasorelaxant peptide originally isolated from human pheochrom ocytoma. The immunohistological distribution was examined of AM in hum an, rat, and porcine tissues using a polyclonal antibody to a fragment comprising C-terminal amino acids 40-52 of human adrenomedullin [AM(4 0-52)NH2]. Al most all of the human pheochromocytoma and normal adrena l medullary cells of all three species were immunostained and found to be intensely positive for AM. Furthermore, AM-immunoreactive cells we re present in the pancreatic islets, gastrointestinal neuroendocrine s ystem, anterior pituitary, and choroid plexus with some degree of inte rspecies heterogeneity. These findings indicate that AM-immunoreactive cells are widely distributed in the endocrine and neuroendocrine syst em, suggesting that AM plays some important role in the control of sys temic and local circulation and also of humoral secretion.