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 t o evaluate the role of OFR and xanthine oxidase in hepatocellular Ca2+ dysr egulation following hemorrhagic shock and resuscitation, Anesthetized rats were bled to a mean arterial blood pressure of 40 mmHg for 60 min and then resuscitated with 60% of shed blood and 3-fold the shed blood volume as lac tated Ringer's for another 60 min. Total Ca2+ uptake (Ca-up(2+)), rate of C a2+ influx (Ca-in(2+)), and membrane Ca2+ flux (Ca-flux(2+)) were determine d in isolated hepatocytes using Ca-45(2+) incubation techniques. Hepatocyte oxidant injury was fluorometrically determined by thiobarbituric acid-reac tive substances, oxidized, and reduced glutathione. Hemorrhage/resuscitatio n significantly increased Ca-up(2+), Ca-in(2+), and Ca-flux(2+) compared wi th sham-operated rats. Continuous administration of superoxide dismutase or catalase (60,000 IU/kg body weight) during resuscitation substantially dec reased Ca-up(2+), Ca-in(2+), Ca-flux(2+), and oxidant injury. Pretreatment with allopurinol (50 mg/kg/day for 2 days) significantly inhibited enhanced plasma xanthine oxidase activity and hepatocyte glutathione oxidation, how ever, it did not prevent hepatocellular Ca2+ dysregulation. These data sugg ested a significant role of oxyradicals in ischemia/reperfusion-induced Ca2 + overload, however, xanthine oxidase activation seemed not to be a main so urce of these radicals.