Adrenomedullin2/intermedin (AM2/IMD) is a novel member of the calcitonin/calcitonin gene-related peptide (CGRP) family. In the present study, we developed a specific radioimmunoassay of human AM2/IMD. Expression of AM2/IMD was studied in the human brain, pituitary, heart and kidney obtained at autopsy by radioimmunoassay and immunocytochemistry. Immunoreactive-AM2/IMD was detected by radioimmunoassay in human brains (range; 0.163-1.495 pmol/g wet weight), pituitaries (4.46+/-0.689 pmol/g wet weight, mean+/-S.E.M, n=3), left ventricles of hearts (0.251+/-0.0321 pmol/g wet weight, n=4), kidneys (3.49+/-1.18 pmol/g wet weight, n=5), and plasma obtained at healthy subjects (24.7+/-1.78 pmol/l, n=3). Reverse-phase high performance liquid chromatography showed that immunoreactive-AM2/IMD in human brain, kidney and plasma extracts were eluted in the position of authentic AM2/IMD. Additional peaks eluted earlier were found in the brain tissue and plasma. Immunocytochemistry showed that immunoreactive-AM2/IMD was localized in paraventricular and supraoptic nuclei of hypothalamus, anterior and posterior lobes of pituitary, cardiomyocytes, pericardial adipocytes, vascular endothelial cells of pericardial veins, and vascular smooth muscle cells of coronary arteries and renal arterioles as well as in renal tubular cells. The present study has shown expression of AM2/IMD in various types of cells in the central nervous system and the cardiovascular system, and suggested possible (patho)physiological roles of AM2/IMD in these systems.