Nitric oxide synthase activity is inducible in rat, but not rabbit alveolar macrophages, with a concomitant reduction in arginase activity.
Alveolar macrophages were obtained by broncho-alveolar lavage of isolated rat and rabbit lungs and cultured (2.5 x 10(6) cells/dish) for 18 h in the absence or presence of bacterial lipopolysaccharides (LPS) alone or in combination with cytokines. Thereafter, accumulation of 3H-citrulline (NO synthase activity) and 3H-ornithine (arginase activity) were determined. During incubation of rat alveolar macrophages with 3H-arginine clear amounts of 3H-citrulline and 3H-ornithine (3.8 and 4.6% of the added 3H-arginine, respectively) were formed and most of these metabolites appeared in the incubation medium (ratios extra-/intracellular of 17 and 70 for 3H-citrulline and 3H-ornithine, respectively). When rat alveolar macrophages had been cultured with LPS the formation of 3H-citrulline was increased about 30-fold and this was accompanied by a reduction in 3H-ornithine formation of about 60%. The effects of LPS were largely attenuated by dexamethasone (10 mumol/l). Inhibition of NO synthase by NG-monomethyl-L-arginine (L-NMMA, 100 mumol/l) in LPS treated alveolar macrophages reduced the formation 3H-citrulline by more than 90% and restored the 3H-ornithine formation. After culturing in the presence of LPS the ratios extra/intracellular of 3H-citrulline and 3H-ornithine were markedly enhanced and this effect was not dexamethasone sensitive.(ABSTRACT TRUNCATED AT 250 WORDS)
Hey
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Department Pharmacology, University of Frankfurt, Germany.
Wessler
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Racké
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D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis* / Q000187:drug effects; D000818:Animals; D001119:Arginase / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D002956:Citrulline / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004790:Enzyme Induction; D005260:Female; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology*; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D019001:Nitric Oxide Synthase; D009573:Nitrites / Q000378:metabolism; D009952:Ornithine / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D019323:omega-N-Methylarginine
D016207:Cytokines; D008070:Lipopolysaccharides; D009573:Nitrites; D019323:omega-N-Methylarginine; D002956:Citrulline; D009569:Nitric Oxide; D003907:Dexamethasone; D001120:Arginine; D009952:Ornithine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D001119:Arginase