Expression of Vasoactive Genes in the Liver during Ischemia/Reperfusion Injury in a Pig Model
Abstracts
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Introduction: Oxidative stress, inflammatory response associated with ischemia/reperfusion injury are well known complications after liver resection and transplantation. They promote microcirculatory dysfunction which limits the function of the organ. Altered liver microcirculation may result from an imbalance in the expression of stress-induced vasoactive mediators. It has been previously shown that constriction of the liver sinusoids is mediated by hepatic stellate cells in which ETA receptors are present at high density. Aim: The goal of our study was to investigate the changes in the expression of genes encoding vasoconstrictors as endothelin-1 (ET-1) and its receptors ETA and ETB in the liver using an ischemia/reperfusion (I/R) pig model. Methods: In the experiments, pigs (n=7) were subjected to 2 h of hepatic ischemia by clamping the vascular pedicles of the whole liver. One hour after reperfusion and on the 5th postoperative day tissue samples were obtained, snap frozen, and mRNA was extracted. Specific primers were designed and to our knowledge for the first time a real-time quantitative RT-PCR (TaqMan) was performed to analyze the expression changes in this model. Gene expression was normalized to beta actin. Results: Present data of our study show a quantitative expression at baseline of 15.2, 495.4, and 2.2 copies/105copies beta actin (Median) for ET-1, ETA, and ETB, respectively. During the first hour after reperfusion ETA receptor expression decreased 44% of baseline to 162.2 (p<0,014). Almost complete recovery was observed on the 5th postoperative day (427.9). In contrast, ETB receptor expression was very low at baseline and did not significantly change during the postoperative observation period. In addition, ET-1 expression was not significantly affected by the ischemia/reperfusion injury. Conclusion: We speculate that the observed decrease of ETA receptor expression in pig liver after ischemia/reperfusion injury may reflect a response of the vascular system maintaining the microcirculation in the postischemic reperfusion period by diminishing the receptor-mediated response to endothelin-1. We now investigate the expression of other mediators specific for vasodilation and the role of ET-1 receptor antagonists in postischemic reperfusion injury of the liver. |
