Human proadrenomedullin N-terminal 20 peptide in pheochromocytoma and normal adrenal medulla.

Proadrenomedullin N-terminal 20 peptide (PAMP) is a novel hypotensive peptide found in adrenomedullin precursor. Using a radioimmunoassay for human PAMP, we purified immunoreactive PAMP (ir-PAMP) from human pheochromocytoma and determined its complete amino acid sequence. The major component of PAMP-like immunoreactivity was found to be PAMP [1-20] NH2 with an amino acid sequence identical to that of the deduced amino acid sequence by cDNA analysis. Both ir-PAMP and ir-adrenomedullin were found to be abundant in normal adrenal medulla as well as pheochromocytoma tissue arising from adrenal medulla, and there was a significantly (p < 0.05) positive correlation between ir-adrenomedullin and ir-PAMP concentrations in these tissues. However, the PAMP/adrenomedullin ratio in pheochromocytoma tissues (0.197 +/- 0.013) was significantly (p < 0.005) lower than that in adrenal medullae (0.384 +/- 0.041). The present data indicate that PAMP is biosynthesized from adrenomedullin precursor, but the biosynthesis or metabolism of PAMP in pheochromocytoma may be different from that of normal adrenal medulla.