DISTRIBUTION AND CHARACTERIZATION OF RAT IMMUNOREACTIVE PROADRENOMEDULLIN N-TERMINAL 20 PEPTIDE (PAMP) AND THE AUGMENTED CARDIAC PAMP IN SPONTANEOUSLY HYPERTENSIVE RAT

Proadrenomedullin N-terminal 20 peptide (PAMP) is a novel hypotensive peptide processed from an adrenomedullin precursor. In this study, hig h concentrations of immunoreactive PAMP (ir-PAMP) were detected in rat cardiac atrium and adrenal gland by the radioimmunoassay (RIA) for ra t PAMP. The mean plasma concentration of rat ir-PAMP was 3.8+/-0.3 fmo l/ml. Analysis in atrium, adrenal gland and plasma with high performan ce liquid chromatographies showed that most ir-PAMP emerged as one maj or peak at the position exactly identical to that of the authentic rat PAMP. We further investigated the tissue and plasma concentrations of rat ir-PAMP in spontaneously hypertensive rat (SHR) to elucidate the role of PAMP in hypertension. The ir-PAMP concentration in heart tissu e of SHR was found to be increased compared with that of the control r at. Especially, the atrial concentration of ir-PAMP of SHR (5.66+/-0.7 8 fmol/mg wet tissue) was significantly higher than that of the contro l (3.29+/-0.22 fmol/mg wet tissue). Cardiac PAMP might have a role for the protection from systemic hypertension.