Contribution of epoxyeicosatrienoic acids to the cerebral blood flow response to hypoxemia

Xiaoguang Liu, Debebe Gebremedhin, David R. Harder, Raymond C. Koehler

Research output: Contribution to journalArticlepeer-review

Abstract

Liu X, Gebremedhin D, Harder DR, Koehler RC. Contribution of epoxyeicosatrienoic acids to the cerebral blood flow response to hypoxemia. J Appl Physiol 119: 1202-1209, 2015. First published March 19, 2015; doi:10.1152/japplphysiol.01043.2014.-Adenosine A2A receptors and ATP-activated K+ (KATP) channels contribute to part of the cerebral vasodilatory response to systemic hypoxia, but other mediators are likely involved. Epoxyeicosatrienoic acids (EETs) are cerebral vasodilators and are released from astrocytes exposed to hypoxia. Moreover, stimulation of metabotropic glutamate receptors (mGluR) produces vasodilation by an EET-dependent mechanism. Here, we tested the hypothesis that EET signaling and mGluR activation contribute to hypoxic vasodilation. Laser-Doppler flow was measured over cerebral cortex of anesthetized rats subjected to stepwise reductions in arterial oxygen saturation to 50-70%. Hypoxic reactivity was calculated as the slope of the change in laser-Doppler flow vs. the reciprocal of arterial oxygen content. Hypoxic reactivity significantly decreased from 9.2±1.9 (±95% confidence interval) in controls with vehicle treatment to 2.6±1.4 with the EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid, to 3.0±1.5 with the EET synthesis inhibitor MS-PPOH, to 1.9±2.3 with the combined mGluR subtype 1 and 5 antagonists 2-methyl-6-(phenylethynyl)pyridine and LY367385, to 5.6±1.2 with the KATP channel inhibitor glibenclamide, and to 5.8±2.3 with the A2A receptor antagonist SCH58261. However, reactivity was not significantly altered by the A2B receptor antagonist MRS1754 (6.7±1.8; P = 0.28 Dunnett's test) or by the 20-hydroxyeicosatetraenoic acid synthesis inhibitor HET0016 (7.5±2.3; P = 0.6). These data indicate that, in addition to the known contributions of A2A receptors and KATP channels to the increase in cerebral blood flow during hypoxia, EETs and mGluRs make a major contribution, possibly by mGluR stimulation and hypoxia-induced release of EETs. In contrast, A2B receptors do not make a major contribution, and 20-hydroxyeicosatetraenoic acid does not significantly limit hypoxic vasodilation.

Original languageEnglish (US)
Pages (from-to)1202-1209
Number of pages8
JournalJournal of applied physiology
Volume119
Issue number10
DOIs
StatePublished - Nov 15 2015

Keywords

  • Cerebral circulation
  • Cytochrome P-450
  • EET
  • Hypoxia
  • Vasodilation

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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