Non-enzymatic nitric oxide synthesis in biological systems

Jay L. Zweier, Alexandre Samouilov, Periannan Kuppusamy

Research output: Contribution to journalArticle

Abstract

Nitric oxide (NO) is an important regulator of a variety of biological functions, and also has a role in the pathogenesis of cellular injury. It had been generally accepted that NO is solely generated in biological tissues by specific nitric oxide synthases (NOS) which metabolize arginine to citrulline with the formation of NO. However, NO can also be generated in tissues by either direct disproportionation or reduction of nitrite to NO under the acidic and highly reduced conditions which occur in disease states, such as ischemia. This NO formation is not blocked by NOS inhibitors and with long periods of ischemia progressing to necrosis, this mechanism of NO formation predominates. In postischemic tissues, NOS-independent NO generation has been observed to result in cellular injury with a loss of organ function. The kinetics and magnitude of nitrite disproportionation have been recently characterized and the corresponding rate law of NO formation derived. It was observed that the generation and accumulation of NO from typical nitrite concentrations found in biological tissues increases 100-fold when the pH falls from 7.4 to 5.5. It was also observed that ischemic cardiac tissue contains reducing equivalents which reduce nitrite to NO, further increasing the rate of NO formation more than 40-fold. Under these conditions, the magnitude of enzyme-independent NO generation exceeds that which can be generated by tissue concentrations of NOS. The existence of this enzyme-independent mechanism of NO formation has important implications in our understanding of the pathogenesis and treatment of tissue injury. Copyright (C) 1999 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)250-262
Number of pages13
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1411
Issue number2-3
DOIs
StatePublished - May 5 1999

Keywords

  • Acidosis
  • Electron paramagnetic resonance
  • Ischemia
  • Nitric oxide imaging
  • Nitric oxide synthesis
  • Nitrite disproportionation

ASJC Scopus subject areas

  • Biophysics

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