Adrenomedullin: a vasoactive and natriuretic peptide with therapeutic potential.

Adrenomedullin is a potent endogenous vasodilating and natriuretic peptide that is similar in structure to calcitonin gene-related peptide (CGRP). The gene involved in the synthesis of adrenomedullin has been localized to a single locus on chromosome 11, with specific sites on the genome to regulate transcription. Adrenomedullin is normally found in human plasma and in other organs. It is thought that one of the clearance sites for this peptide is in the pulmonary circulation. Endothelial cells are assumed to be one of the major sources of plasma adrenomedullin. Adrenomedullin is an important factor in regulating local and systemic vascular tone, by its activity as an autocrine/paracrine and circulating hormone. Depending on the site of action, adrenomedullin seems to bind to a CGRP receptor and send signals by either cyclic adenosine monophosphate or nitric oxide. From the results of experiments in animals, it has become clear that adrenomedullin's effects are species-specific. However, what is commonly seen with adrenomedullin is peripheral vasodilatation, a positive inotropic action, increased cardiac output, and increased stroke volume. In addition, adrenomedullin has actions in the brain, lungs, and kidneys to regulate regional hemodynamics. With these activities defined, recent studies have suggested a potential therapeutic role for adrenomedullin.