HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kanu, A. Articles by Leffler, C. W. Search for Related Content PubMed PubMed Citation Articles by Kanu, A. Articles by Leffler, C. W.

---

ORIGINAL RESEARCH ARTICLE

Cyclooxygenase Products Stimulate Carbon Monoxide Production by Piglet Cerebral Microvessels

Laboratory for Research in Neonatal Physiology, Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163

To whom requests for reprints should be addressed at ¹ Department of Physiology, 894 Union Avenue, Memphis, TN 38163. E-mail: cleffler{at}physio1.utmem.edu

Products of arachidonic acid (AA) metabolism by cyclooxygenase (Cox) are important in regulation of neonatal cerebral circulation. The brain and cerebral microvessels also express heme oxygenase (HO) that metabolizes heme to carbon monoxide (CO), biliverdin, and iron. The purpose of this study in newborn pig cerebral microvessels was to address the hypothesis that Cox products affect HO activity and HO products affect Cox activity. AA (2.0–20 µM) increased prostaglandin E₂ (PGE₂) measured by radioimmunoassay (RIA) and also CO measured by gas chromatography/mass spectrometry (GC/MS). Further, 10^–4 M indomethacin, which inhibited Cox, reduced both AA and heme-induced CO production. Conversely, neither exogenous 2 x 10^–6 M heme, which markedly increased CO production, nor the inhibitor of HO, chromium mesoporphyrin, altered PGE₂ synthesis. Because AA metabolism by Cox generates both prostanoids and superoxides, we determined the effects of the predominant prostanoid and superoxide on CO production. Although PGE₂ caused a small increase in CO production, xanthine oxidase plus hypoxanthine, which produces superoxide, strongly stimulated the production of CO by cerebral microvessels. This increase was mildly attenuated by catalase. These data suggest that Cox-catalyzed AA metabolites, most likely superoxide and/or a subsequent reactive oxygen species, increase cerebrovascular CO production. This increase seems to be caused, at least in part, by the elevation of HO-2 catalytic activity. Conversely, Cox activity is not affected by HO-catalyzed heme metabolites. These data suggest that some cerebrovascular functions attributable to Cox activity could be mediated by CO.

Key Words: cerebrovascular circulation • heme oxygenase • reactive oxygen species

This article has been cited by other articles:

				C. W. Leffler, H. Parfenova, A. L. Fedinec, S. Basuroy, and D. Tcheranova Contributions of astrocytes and CO to pial arteriolar dilation to glutamate in newborn pigs Am J Physiol Heart Circ Physiol, December 1, 2006; 291(6): H2897 - H2904. [Abstract] [Full Text] [PDF]

				A. Kanu, J. Whitfield, and C. W. Leffler Carbon monoxide contributes to hypotension-induced cerebrovascular vasodilation in piglets Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2409 - H2414. [Abstract] [Full Text] [PDF]