Secretion of proadrenomedullin N-terminal 20 peptide from cultured neonatal rat cardiac cells

Abstract

Proadrenomedullin N-terminal 20 peptide (PAMP) is generated from post-transcriptional enzymatic processing of a 185-amino acid precursor for adrenomedullin (AM), a potent vasodilator peptide. We have reported that AM is secreted from cultured neonatal rat cardiac myocytes and fibroblasts, and that secreted AM modulates the growth of these cells; however, it is unknown whether or not the cardiac cells produce PAMP. In this study, we examined the production of PAMP in cultured neonatal rat cardiac myocytes and fibroblasts. Both the cardiac myocytes and fibroblasts cultured with serum-free media secreted PAMP time-dependently at rates of 5.7±0.9 fmol/10 5 cells/40 h and 8.4±0.7 fmol/5×10 4 cells/48 h (mean±SD), respectively. Reverse-phase high performance liquid chromatography showed that immunoreactive PAMP secreted from these cells was identical to PAMP[1-20], a whole active molecule. PAMP and AM secretions were significantly (P<0.01) stimulated by 10 −6 mol/L angiotensin II (Ang II) and 10% fetal bovine serum (FBS) in myocytes and fibroblasts, whereas the ratio of PAMP to AM secretion in the myocytes was smaller than that of the fibroblasts. These results suggest that PAMP is secreted along with AM from rat cardiac myocytes and fibroblasts, and the secretion is augmented by the growth-promoting stimuli of Ang II and FBS for these cells.