Characterization of immunoreactive adrenomedullin in human plasma and urine

Adrenomedullin(AM) is a novel vasodilator peptide recently isolated from pheochromocytoma. Using a specific and sensitive radioimmunoassay for human AM, we have characterized immunoreactive AM in human plasma and urine. Patients with chronic renal failure had about five-fold higher plasma immunoreactive AM levels than normal subjects, which did not change before and after hemodialysis. Immunoreactive AM was present in normal human urine, whose concentrations were about six-fold greater than those in human plasma. Reverse-phase HPLC of human plasma and urine revealed that immunoreactive AM emerged as a single peak at a position identical to that of authentic human AM(1-52). These data suggest that circulating AM is cleared by the kidney and urinary excretion of AM may be derived from glomerular filtration and/or its renal production.