Increased susceptibility to oxidant injury in hepatocytes from rats with intra-abdominal hypertension

BACKGROUND: Intra-abdominal hypertension leads to visceral organ hypoperfusion, and subsequent decompression may cause ischemia-reperfusion, releasing toxic metabolites. This study focuses on the effect of intra-abdominal hypertension on hepatic antioxidant store and the susceptibility of hepatocytes to oxidant injury. METHODS: Sprague-Dawley rats (150-180 g) were acclimatized to an environment for 3 days and then divided into two groups according to challenge based on intra-abdominal pressure (0 and 30 cm H2O for control and experimental groups, respectively). After a 90-minute challenge, the rats underwent immediate laparotomy for decompression; after a further 30 minutes, one fragment of liver from the lingual lobe (>0.1 g) was excised to measure glutathione (GSH) in vivo before portal vein perfusion. After hepatocyte isolation (viability rate > 85%), the cell density was set at 1 x 10/mL for each well. The samples were cultured in an incubator for 12 hours, after which varying concentrations of t-butyl hydroperoxide (TBHP) (0.0, 0.5, 1.0, and 2.0 mmol/L) were added into the wells. After another 5-hour incubation, the total store of intracellular GSH in vitro (GSHVT) and the hepatocyte survival rates were measured for different groups of TBHP challenge using GSH assay and MTT kits. RESULTS: The control and experimental groups consisted of 10 and 8 rats, respectively, that successfully completed the entire experimental procedure. Compared with the control group, the in vivo GSH store was significantly reduced after the intra-abdominal pressure challenge (mean +/- SE, 968.1 +/- 63.5 vs. 1,581.0 +/- 115.3 nmol/g of protein; p = 0.001). After the hepatocyte isolation, the GSHVT stores at various TBHP concentrations in the experimental rats were also similarly and significantly decreased relative to the control animals (894.4 +/- 56.4, 804.2 +/- 118.4, 586.9 +/- 86.6, and 410.2 +/- 87.4 nmol/g of protein vs. 1,282.2 +/- 112.0, 1,156.6 +/- 91.0, 995.2 +/- 92.7, and 866.8 +/- 62.4 nmol/g of protein for TBHPs of 0.0, 0.5, 1.0, and 2.0 mmol/L, respectively; all p < 0.05). Moreover, from photocytometry, the hepatocyte survival rates were significantly reduced for the experimental rats compared with the control animals after challenge with various TBHP concentrations (survival was 100%, 91.1%, 81.3%, and 72.8% vs. 100%, 99.2%, 95.0%, and 88.2%, respectively, for TBHPs of 0.0, 0.5, 1.0, and 2.0 mmol/L; p < 0.05 for the last two). CONCLUSION: This animal study demonstrated that intra-abdominal hypertension and subsequent decompression deplete the total in vivo GSH store in rat livers, probably via the mechanism of ischemia-reperfusion injury, and the GSHVT after hepatocyte isolation, which makes the isolated hepatocytes of rats more susceptible to oxidant challenge.