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This Article Full Text Full Text (PDF) All Versions of this Article: 294/5/G1219    most recent 00527.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Lee, S. H. Articles by Clemens, M. G. PubMed PubMed Citation Articles by Lee, S. H. Articles by Clemens, M. G.

LIVER AND BILIARY TRACT

Differential mechanisms of hepatic vascular dysregulation with mild vs. moderate ischemia-reperfusion

Department of Biology, University of North Carolina at Charlotte, Charlotte, North Carolina

Submitted 13 November 2007 ; accepted in final form 6 March 2008

Endotoxemia produces hepatic vascular dysregulation resulting from inhibition of endothelin (ET)-stimulated NO production. Mechanisms include overexpression of caveolin-1 (Cav-1) and altered phosphorylation of endothelial nitric oxide (NO) synthase (NOS; eNOS) in sinusoidal endothelial cells. Since ischemia-reperfusion (I/R) also causes vascular dysregulation, we tested whether the mechanisms are the same. Rats were exposed to either mild (30 min) or moderate (60 min) hepatic ischemia in vivo followed by reperfusion (6 h). Livers were harvested and prepared into precision-cut liver slices for in vitro analysis of NOS activity and regulation. Both I/R injuries significantly abrogated both the ET-1 (1 µM) and the ET_B receptor agonist (IRL-1620, 0.5 µM)-mediated stimulation of NOS activity. 30 min I/R resulted in overexpression of Cav-1 and loss of ET-stimulated phosphorylation of Ser1177 on eNOS, consistent with an inflammatory response. Sixty-minute I/R also resulted in loss of ET-stimulated Ser1177 phosphorylation, but Cav-1 expression was not altered. Moreover, expression of ET_B receptors was significantly decreased. This suggests that the failure of ET to activate eNOS following 60-min I/R is associated with decreased protein expression consistent with ischemic injury. Thus hepatic vascular dysregulation following I/R is mediated by inflammatory mechanisms with mild I/R whereas ischemic mechanisms dominate following more severe I/R stress.

liver microcirculation; endothelial nitric oxide synthase; endothelin-1; precision-cut liver slices