ACCELERATED COMMUNICATION Induction of L-Arginine Transport Is Inhibited by Atrial Natriuretic Peptide: A Peptide Hormone as a Novel Regulator of Inducible Nitric-Oxide Synthase Substrate Availability

Background: The inducible nitric-oxide synthase (iNOS) syn-thesizes NO from L-arginine. Availability of L-arginine is main-tained by a lipopolysaccharide (LPS)-induced induction of the CAT-2B amino acids transporter. Recently, we could show that the cardiovascular hormone atrial natriuretic peptide (ANP) in-hibits the induction of iNOS in LPS-stimulated macrophages via its guanylate cyclase-coupled A-receptor. Purpose: To inves-tigate whether ANP exerts an effect on LPS-induced L-arginine uptake. Methods: Murine bone marrow derived macrophages were activated with LPS (1 g/ml, 20 h) in the presence or absence of ANP or C-type natriuretic peptide (CNP). L-Arginine transport was determined by measuring the uptake of L-[3H]arginine. L-[3H]Arginine influx was also determined in LPS-activated cells in the presence of NG-monomethyl-L-argi