Abstract: According to the present invention, adrenomedullin which is a novel peptide having a hypotensive effect; proadrenomedullin N-terminal 20 peptide (proAM-N20) corresponding to an amino acid sequence of an N-terminus of proadrenomedullin, having a catecholamine secretion inhibitory effect; proadrenomedullin N-terminal 10-20 peptide (proAM-N(10-20)) having a Na channel inhibitory effect, and a gene encoding these peptides are provided. In addition, according to the present invention, these peptides in a sample containing adrenomdullin or proAM-N20 in an unknown amount can be quantified by using an antibody against adrenomedullin, proAM-N20, or its fragment.