Novel distribution of adrenomedullin-immunoreactive cells in human tissues

Adrenomedullin (AM) is a novel hypotensive and vasodilator peptide. We prev iously examined the localization of AM in human, rat, and porcine tissues u sing a polyclonal antibody against synthetic human AM[40-52]. We demonstrat ed that AM is widely distributed in the endocrine and neuroendocrine system s, but not in the heart, kidney, or blood vessels, although high levels of AM mRNA were detected in the latter tissues. In this study, we further inve stigated the distribution of AM by using two newly developed monoclonal ant ibodies against synthetic human AM peptides, [12-25] and [46-52]. AM immuno reactivity was observed in cardiac myocytes, vascular smooth muscle cells, endothelial cells, and renal distal and collecting tubules. In addition, AM -immunoreactive (IR) cells were found in mucosal and glandular epithelia of the digestive, respiratory, and reproductive systems, as well as the endoc rine and neuroendocrine systems. These findings indicate that AM-IR cells a re more widely distributed in human tissues and suggest that AM might play multiple biological roles in humans.