 The precursor, called preproadrenomedullin, consists of 185 amino acids and can be cleaved by plasma kallikrein at the Lys-Arg and Arg-Arg sites.By RNA-blot analysis, human adrenomedullin mRNA was found to be expressed in all tissues, and most highly expressed in the placenta, fat cells, lung, pancreatic islets, smooth muscle, and skin.The human AM gene is localized to a single locus on Chromosome 11 with 4 exons and 3 introns.