Endotoxin triggers the expression of an inducible isoform of nitric oxide synthase and the formation of peroxynitrite in the rat aorta in vivo

Csaba Szabó, Andrew L. Salzman, Harry Ischiropoulos

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    226 Scopus citations


    The free radicals nitric oxide (·NO) and superoxide (O2-) are known to react to form peroxynitrite (ONOO-), a highly reactive species. Peroxynitrite has been suggested to play an important role in the cellular damage associated with the overproduction of ·NO, but there are very limited data regarding its in vivo formation. Here we demonstrate that injection of endotoxin into rats leads to the expression of an inducible isoform of ·NO synthase (iNOS) in the thoracic aorta at 6 h and an increase in the circulating levels of nitrite/nitrate. Moreover, at the same time point, there is a marked increase in the immunoreactivity of nitrotyrosine, a marker of peroxynitrite in the aorta. The formation of nitrotyrosine was prevented by inhibiting the activity of NOS by NG-methyl-l-arginine in vivo. Our data suggest that during endotoxin shock, part of ·NO, produced following the induction of iNOS, is converted into peroxynitrite in the vicinity of large blood vessels. The demonstration of the in vivo formation of peroxynitrite at sites of ·NO overproduction may necessitate the development of novel and additional approaches for limiting or preventing ·NO-related cytotoxic or vasodilatory actions during circulatory shock.

    Original languageEnglish (US)
    Pages (from-to)235-238
    Number of pages4
    JournalFEBS Letters
    Issue number3
    StatePublished - Apr 24 1995



    • Contraction
    • Immunohistochemistry
    • Nitric oxide
    • Nitrotyrosine
    • Peroxynitrite
    • Septic shock
    • Superoxide

    ASJC Scopus subject areas

    • Biophysics
    • Structural Biology
    • Biochemistry
    • Molecular Biology
    • Genetics
    • Cell Biology

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