. Cytochrome P-450 metabolites in endothelin-stimulated cardiac hormone secretion. Am J Physiol Regul Integr Comp Physiol 286: R888-R893, 2004. First published January 8, 2004 10.1152/ ajpregu.00482.2003.-We examined the role of cytochrome P-450-arachidonate (CYP450-AA) metabolites in endothelin-1 (ET-1)-stimulated atrial natriuretic peptide (ANP) and pro-ANP-(1-30) secretion from the heart. 17-Octadecynoic acid (17-ODYA, 10 Ϫ5 M) significantly inhibited ANP secretion stimulated by ET-1 (10 Ϫ8 M) in the isolated perfused rat atria and inhibited pro-ANP-(1-30) secretion stimulated by ET-1 (10 Ϫ8 M) or 20-hydroxyeicosatetraenoic acid in cultured neonatal rat ventricular myocytes (NRVM). In NRVM, 17-ODYA significantly (P Ͻ 0.05) increased secretion of cAMP but had no significant effect on the secretion of cGMP from NRVM. Staurosporine, an inhibitor of protein kinase C, completely blocked the inhibitory action of 17-ODYA, whereas a protein kinase A inhibitor, H-89 (5 ϫ 10 Ϫ5 M), did not significantly attenuate the effects of 17-ODYA. The results show that the inhibitory action of 17-ODYA on ET-1-augmented ANP secretion is mediated through cAMP and suggest that CYP450-AA may play an important role in ET-1-induced cardiac hormone secretion.endothelin-1; 20-hydroxyeicosatetraenoic acid; 17-octadecynoic acid; nitric oxide; protein kinase A; protein kinase C; atrial natriuretic peptide; pro-ANP-(1-30); cardiac hypertrophy THE MAMMALIAN HEART SYNTHESIZES and secretes a family of peptides that has potent diuretic, natriuretic, and vascular smooth muscle relaxant effects as well as complex interactions with the hormonal and nervous systems (18,23).Atrial natriuretic peptide (ANP) is secreted by the heart in response to increased atrial stretch (2, 4) such as would typically be produced by an increase in blood volume. ANP is initially stored in granules in the heart as a 126-amino acid prohormone (pro-ANP). During the secretion process (4, 3, 10), the pro-ANP molecule is cleaved to form ANP, the 28-amino acid COOHterminus of pro-ANP, and several NH 2 -terminal prohormone peptides, pro-ANP-(1-30), -(31-67), and -(79-98). Our recent data suggest that pro-ANP-(1-30) also increases sodium excretion and plays a role in blood volume and blood pressure regulation (5).Numerous factors have been shown to modulate the secretion of ANPs, including endothelin-1 (ET-1), a potent vasoconstrictor synthesized and secreted by endothelial cells (8).ET-1 has also been shown to have potent hypertrophy-promoting effects in a variety of mammalian cells, including vascular smooth muscle cells, cardiomyocytes (13), and fibroblasts (25). Various models of cardiac hypertrophy have demonstrated increased ET expression and secretion in the heart (13). ET-1 has been shown to be a potent stimulus for the hypertrophy of neonatal rat ventricular myocytes (NRVM) in vitro (24). In addition, ET-1 increases cell contraction frequency (14) and protein synthesis and modulates stretch-induced ANP release (21,20) and gene expression (8,9,12,13,19). Skvorak et al...