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  • Title: Regulation of the rate of synthesis of nitric oxide by Mg(2+) and hypoxia. Studies in rat heart mitochondria.
    Author: Manzo-Avalos S, Pérez-Vázquez V, Ramírez J, Aguilera-Aguirre L, González-Hernández JC, Clemente-Guerrero M, Villalobos-Molina R, Saavedra-Molina A.
    Journal: Amino Acids; 2002 Jun; 22(4):381-9. PubMed ID: 12107764.
    Abstract:
    In isolated rat heart mitochondria, L-arginine is oxidized by a nitric oxide synthase (mtNOS) achieving maximal rates at 1 mM L-arginine. The NOS inhibitor N(G)-nitro-L-arginine methyl ester (NAME) inhibits the increase in NO production. Extramitochondrial free magnesium inhibited NOS production by 59% at 3.2 mM. The mitochondrial free Mg(2+) concentration increased to different extents in the presence of L-arginine (29%), the NO donor (S-nitroso-N-acetylpenicillamine) (105%) or the NOS inhibitors L-NAME (48%) or N(G)-nitro-L-arginine methyl ester, N(G)-monomethyl-L-arginine (L-NMMA) (53%). Under hypoxic conditions, mtNOS activity was inhibited by Mg(2+) by up to 50% after 30 min of incubation. Reoxygenation restored the activity of the mtNOS to pre-hypoxia levels. The results suggest that in heart mitochondria there is an interaction between Mg(2+) levels and mtNOS activity which in turn is modified by hypoxia and reoxygenation.
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