title: Nitric oxide derived from L-arginine impairs cytoplasmic pH regulation by vacuolar-type H+ ATPases in peritoneal macrophages.
abstract: The ability of macrophages (Møs) to function within an acidic environment has been shown to depend on cytoplasmic pH (pHi) regulation by vacuolar-type H+ ATPases. Møs metabolize L-arginine via an oxidative pathway that generates nitric oxide, nitrate, and nitrite. Since each of these products could potentially inhibit vacuolar-type H+ ATPases, we investigated the effect of L-arginine metabolism on Mø pHi regulation in thioglycolate-elicited murine peritoneal Møs. H+ ATPase-mediated pHi recovery from an imposed cytoplasmic acid load was measured fluorometrically. When Møs were incubated with L-arginine (0.25-2.0 mM), their rate of pHi recovery declined progressively from 2 to 6 h of incubation. By contrast, the recovery rate of cells incubated in arginine-free medium remained stable over the same period. The impairment of pHi recovery was specific for L-arginine, and was blocked competitively by NG-monomethyl-L-arginine, demonstrating its dependence on L-arginine metabolism. In addition, the inhibition of pHi recovery was enhanced by lipopolysaccharide, an agent known to stimulate L-arginine metabolism by Møs. Scavenging the L-arginine metabolite nitric oxide with either ferrous sulphate or ferrous myoglobin prevented the inhibition of pHi recovery, implying that L-arginine-derived nitric oxide was the species responsible for the inhibition. This concept was supported by the finding of elevated nitrite levels in the supernatant of cells incubated in L-arginine. Furthermore, incubation of Møs with sodium nitroprusside mimicked the L-arginine-dependent inhibition of H+ ATPase activity. Treatment with the cyclic GMP analogue, 8-bromoguanosine 3':5'-cyclic monophosphate, similarly impaired Mø pHi recovery, suggesting that a nitric oxide-stimulated elevation of cyclic GMP may contribute to the L-arginine-dependent inhibition of pHi regulation.
authors.affiliation: Department of Surgery, Toronto General Hospital, Ontario, Canada.
authors.forename: C J
authors.initials: CJ
authors.lastname: Swallow
authors.forename: S
authors.initials: S
authors.lastname: Grinstein
authors.forename: R A
authors.initials: RA
authors.lastname: Sudsbury
authors.forename: O D
authors.initials: OD
authors.lastname: Rotstein
mesh_terms: D000136:Acid-Base Equilibrium; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D001639:Bicarbonates / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology; D006152:Cyclic GMP / Q000502:physiology; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008070:Lipopolysaccharides; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009569:Nitric Oxide / Q000494:pharmacology*; D010529:Peritoneal Cavity / Q000166:cytology; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D014617:Vacuoles / Q000201:enzymology*; D019323:omega-N-Methylarginine
chemical_list: D001639:Bicarbonates; D008070:Lipopolysaccharides; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D012964:Sodium; D000242:Cyclic AMP; D006180:Proton-Translocating ATPases; D006152:Cyclic GMP