Oxidative and proteolytic cell injury: comparison of susceptibility of isolated rat pancreatic acinar cells versus isolated rat hepotocytes

Abstract

The present study compares the susceptibility of isolated rat pancreatic acinar cells versus rat hepatocytes against xanthine oxidase-mediated oxidative injury and against proteolytic attack. Cells were incubated in solutions containing either xanthine oxidase, hypoxanthine, and chelated iron (XOD/HX solution), or various concentrations of H 2O 2 or active trypsin and chymotrypsin. Cell viability was assessed by uptake of trypan blue realease of LDH. The XOD/HX system caused a rapid generation of radicals during a few initial minutes as assessed by the deoxyribose assay, whereas the resulting damage to either type of cells developed slowly over several hours. This indication for effective cellular antioxidant defenses was supported by the finding that addition of both cell types to the XOD/HX solution significantly reduced the oxidation of deoxyribose seen in cell-free studies, There were, however, also striking differences in the behaviour of acinar cells and hepatocytes against oxidative and proteolytic attack. Pancreatic cells were more susceptible to oxidative stress than hepatocytes, whereas hepatocutes were more susceptible to proteolytic damage. In both cell types chymotrypsin caused significantly greater injury than did trypsin. This difference was small for hepatocytes and large for pancreatic cells. In both cell types catalase and glutathione peroxidase significantly reduced oxidative cell damage, suggesting that a major part of damage was mediated by H 2O 2 and hydroxyl radicals. Both cell types were also susceptible to direct damage by H 2O 2; again the susceptibility cells was greater than that of hepatocytes. In conclusion, the present results demonstrate that pancreatic cells and hepatocytes are susceptible to oxidative stress, although they have effective antioxidant capacities which are similar for both cell types. The pancreatic cell - probably due to a its large antitrypsin capacity - was markedly less susceptible to direct damage by proteases when compared with the hepatocyte. However, the high concentrations of proteases in the acinar cell might explain why these cells are more susceptible to oxidative stress than the hepatocyte, since a major part of xanthine oxidase may be generated extracellularly due to leakage of proteases from already damaged cells.