[Adrenomedullin receptors].

Adrenomedullin(AM) is a potent hypotensive peptide originally isolated from human pheochromocytoma. AM exerts various biological actions such as vasodilation, bronchodilation and natriuresis, by stimulating cAMP production and increasing free Ca2+ levels through the specific receptors. Although an orphan receptor cloned from rat lung, which contained seven transmembrane domains, was proved to be one of the AM receptors, it is now considered by many studies that other receptor subtypes should be present. The precise signal transduction mechanism for the AM receptor is not fully elucidated yet, but it is supposed that AM acts against proliferative changes of vascular and mesangial cells as seen in hypertensive states, at least partly by inhibiting the MAP kinase pathway. Further studies on the AM receptor subtypes and their intracellular signaling mechanisms are needed to clarify the role of AM in various pathophysiological conditions.