Ischemic postconditioning decreases iNOS gene expression but ischemic preconditioning ameliorates histological injury in a swine model of extended liver resection

Background: Both pre- and postconditioning have been shown to protect the liver parenchyma from ischemia/reperfusion (I/R) injury during hepatectomy by altering the production of NO. However, to date there is no study to compare their effect on the inducible nitric oxide synthase ( iNOS ) and endothelial nitric oxide synthase ( eNOS ) gene expression, who are the main modulators in the pathway of NO during the acute phase of I/R injury. Methods: We designed a prospective experimental cohort comprising of three groups (sham group—SG, preconditioning—PrG and postconditioning group—PoG) and consisting of 10 animals per group. All animals underwent extended hepatectomy (70%) under prolonged warm ischemia either after preconditioning or followed by postconditioning or without any protective maneuver (SG). Following reperfusion blood samples and liver biopsies were obtained at the start of reperfusion (0 hours), at 6 and 12 hours post reperfusion. iNOS and eNOS gene expression was assessed on liver tissue by polymerase chain reaction (PCR); in addition, the extent of hepatocellular injury was histologically assessed. Results: At the beginning of reperfusion iNOS expression was significantly reduced in the PoG in comparison to the SG (Kruskal-Wallis test, P=0.012; Mann-Whitney U test, P Conclusions: PoG appeared to decrease iNOS overexpression more effectively than PrG in comparison to animals who have undergone no protective maneuver (SG). However, PrG was more effective than PoG in ameliorating the hepatocellular injury observed at 12 hours after the ischemic insult.