Mechanisms of vasodilatation induced by nitrite instillation in intestinal lumen: Possible role of hemoglobin

Andrey V. Kozlov, Giuseppina Costantino, Babak Sobhian, Laszlo Szalay, Fraz Umar, Hans Nohl, Soheyl Bahrami, Heinz Redl

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

It has been shown that nitrite can be reduced to nitric oxide (NO) in intestine and a number of other tissues and released into the blood to form nitrosylhemoglobin (NO-Hb), existing in an equilibrium with S-nitrosohemoglobin. The latter has been suggested to be an NO transporter to distant organs. The aim of this study was to define the pathway of nitrite reduction to form NO in intestinal wall and to estimate whether this pathway has an effect on peripheral circulation. We have shown that in rat intestine at pH 7.0 70% of nitrite is converted to NO in mitochondria. At pH 6.0, nonenzymatic nitrite reduction becomes as efficient as the mitochondrial pathway. To prove whether the NO formed from nitrite in intestine can induce vasodilatation, sodium nitrite was instilled into intestinal lumen and the concentration of NO formed and diffused into the blood was followed by measuring of NO-Hb complex formation. We found that the concentration of NO-Hb gradually increases with the increase of nitrite concentration in intestinal lumen. However, it was not always accompanied by a decrease in systemic blood pressure. Blood pressure dropped down only after NO-Hb reached a threshold concentration of ∼10 μM. These data show that NO-Hb cannot provide enough NO for vasodilatation if the concentration of NO bound to Hb is < 10 μM. The exact mechanism underlying vasodilatation observed when the concentration of NO-bound Hb was > 10 μM is, however, not clear yet and requires further studies.

Original languageEnglish
Pages (from-to)515-521
Number of pages7
JournalAntioxidants and Redox Signaling
Volume7
Issue number3-4
DOIs
Publication statusPublished - Mar 1 2005

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology

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