Constitutive nitric oxide production by rat alveolar macrophages

• Published in: American journal of physiology. Lung cellular and molecular physiology Vol. 274; no. 3; pp. 360 - L368
• Main Authors: Miles, P. R, Bowman, L, Rengasamy, A, Huffman, L
• Format: Journal Article
• Language: English
• Published: United States 01.03.1998
• Subjects: Adenosine Triphosphate - metabolism; Animals; Calcimycin - pharmacology; Calcium - metabolism; Endothelium, Vascular - drug effects; Endothelium, Vascular - enzymology; Enzyme Induction; Enzyme Inhibitors - pharmacology; Ionophores - pharmacology; Lactic Acid - metabolism; Macrophages - drug effects; Macrophages - metabolism; Magnesium - metabolism; Male; NG-Nitroarginine Methyl Ester - pharmacology; Nitric Oxide - biosynthesis; Nitric Oxide Synthase - antagonists & inhibitors; Nitric Oxide Synthase - biosynthesis; Nitric Oxide Synthase Type III; omega-N-Methylarginine - pharmacology; Ornithine - analogs & derivatives; Ornithine - pharmacology; Pulmonary Alveoli - drug effects; Pulmonary Alveoli - metabolism; Rats; Rats, Sprague-Dawley
• ISSN: 1040-0605; 0002-9513; 1522-1504
• DOI: 10.1152/ajplung.1998.274.3.L360

1  Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown 26505; and 2  Department of Physiology, West Virginia University School of Medicine, Morgantown, West Virginia 26506 Results from previous studies suggest that alveolar macrophages must be exposed to inflammatory stimuli to produce nitric oxide (· NO). In this study, we report that naive unstimulated rat alveolar macrophages do produce · NO and attempt to characterize this process. Western blot analysis demonstrates that the enzyme responsible is an endothelial nitric oxide synthase (eNOS). No brain or inducible NOS can be detected. The rate of · NO production is ~0.07 nmol · 10 6 cells 1 · h 1 , an amount that is less than that produced by the eNOS found in alveolar type II or endothelial cells. Alveolar macrophage · NO formation is increased in the presence of extracellular L -arginine, incubation medium containing magnesium and no calcium, a calcium ionophore (A-23187), or methacholine. · NO production is inhibited by N G -nitro- L -arginine methyl ester ( L -NAME) but not by N G -nitro- L -arginine, L - N 5 -(1-iminomethyl)ornithine hydrochloride, or aminoguanidine. Incubation with ATP, ADP, or histamine also inhibits · NO formation. Some of these properties are similar to and some are different from properties of eNOS in other cell types. Cellular · NO levels do not appear to be related to ATP or lactate content. Alveolar macrophage production of · NO can be increased approximately threefold in the presence of lung surfactant or its major component, dipalmitoyl phosphatidylcholine (DPPC). The DPPC-induced increase in · NO formation is time and concentration dependent, can be completely inhibited by L -NAME, and does not appear to be related to the degradation of DPPC by alveolar macrophages. These results demonstrate that unstimulated alveolar macrophages produce · NO via an eNOS and that lung surfactant increases · NO formation. This latter effect may be important in maintaining an anti-inflammatory state in vivo. lung surfactant; dipalmitoyl phosphatidylcholine; nitric oxide synthase