Adrenomedullin (11-26): a novel endogenous hypertensive peptide isolated from bovine adrenal medulla.

Adrenomedullin (AM) is a potent hypotensive peptide originally isolated from pheochromocytoma tissue. Both the ring structure and the C-terminal amide structure of AM are essential for its hypotensive activity. We have developed an RIA which recognizes the ring structure of human AM. Using this RIA, we have characterized the molecular form of AM in bovine adrenal medulla. Gel filtration chromatography revealed that three major peaks of immunoreactive AM existed in the adrenal medulla. The peptide corresponding to Mr 1500 Da was further purified to homogeneity. The peptide was determined to be AM (11-26) which has one intramolecular disulfide bond. Amino acid sequences of bovine AM and its precursor were deduced from the analyses of cDNA encoding bovine AM precursor. The synthetic AM (11-26) produced dose-dependent strong pressor responses in unanesthetized rats in vivo. The hypertensive activity lasted about one minute, and a dose dependent increase in heart rate was also observed. The present data indicate that AM (11-26) is a major component of immunoreactive AM in bovine adrenal medulla and shows pressor activity.