Immunoreactive proadrenomedullin N-terminal 20 peptide in human tissue, plasma and urine.

Proadrenomedullin N-terminal 20 peptide (PAMP) is a candidate for a novel biologically active peptide processed from proadrenomedullin. This study clearly demonstrates the existence of PAMP in vivo that had been deduced from analysis of cDNA. To identify PAMP in vivo, we established a radioimmunoassay for PAMP and characterized immunoreactivities in human tissue, plasma and urine. Half maximal inhibition of the assay was observed at 10 fmol/tube. A high concentration of immunoreactive PAMP was found in adrenal medulla (18.4 +/- 8.95 fmol/mg, mean +/- S.D.) and pheochromocytoma tissue (12.3 +/- 9.82 fmol/mg) where the concentrations are comparable to that of adrenomedullin. As determined by three different kinds of chromatography, most of the immunoreactive peptide in pheochromocytoma was eluted at a position exactly identical to that of synthetic PAMP. Further, considerable concentration of immunoreactive PAMP was found in human plasma and urine. The present data indicate that PAMP as well as adrenomedullin is processed from an adrenomedullin precursor.