Oxyradical-mediated hepatocellular Ca2+ alterations during hemorrhagic shock and resuscitation

Both altered Ca2+ homeostasis and injury by oxygen-free radicals (OFR) are pivotal mechanisms of cellular dysfunction. The purpose of this study was to evaluate the role of OFR and xanthine oxidase in hepatocellular Ca2+ dysregulation following hemorrhagic shock and resuscitation. Anesthetized rats were bled to a mean arterial blood pressure of 40 mm Hg for 60 min and then resuscitated with 60% of shed blood and 3-fold the shed blood volume as lactated Ringer's for another 60 min. Total Ca2+ uptake (Ca2+(up)), rate of Ca2+ influx (Ca2+(in)), and membrane Ca2+(flux) (Ca2+(flux)) were determined in isolated hepatocytes using 45Ca2+ incubation techniques. Hepatocyte oxidant injury was fluorometrically determined by thiobarbituric acid-reactive substances, oxidized, and reduced glutathione. Hemorrhage/resuscitation significantly increased Ca2+(up), Ca2+(in), and Ca2+(flux) compared with sham-operated rats. Continuous administration of superoxide dismutase or catalase (60,000 IU/kg body weight) during resuscitation substantially decreased Ca2+(up), Ca2+(in), Ca2+(flux), and oxidant injury. Pretreatment with allopurinol (50 mg/kg/day for 2 days) significantly inhibited enhanced plasma xanthine oxidase activity and hepatocyte glutathione oxidation, however, it did not prevent hepatocellular Ca2+ dysregulation. These data suggested a significant role of oxyradicals in ischemia/reperfusion-induced Ca2+ overload, however, xanthine oxidase activation seemed not to be a main source of these radicals.