INCREASED CYTOSOLIC CA2-INDUCED ALTERATIONS OF THE ULTRASTRUCTURE ANDTHE ENERGY-METABOLISM OF ISOLATED RAT PANCREATIC ACINAR-CELLS( AMPLIFIES OXYGEN RADICAL)

Background: Oxygen radicals have been implicated as important mediator s in the early pathogenesis of acute pancreatitis, but the mechanism b y which they produce pancreatic tissue injury remains unclear. We have , therefore, investigated the effects of oxygen radicals on isolated r at pancreatic acinar cells as to the ultrastructure, cytosolic Ca2+ co ncentration and energy metabolism. Methods: Acinar cells were exposed to an oxygen radical-generating system consisting of xanthine oxidase, hypoxanthine and chelated iron ions. Cell injury was assessed by LDH release and electron microscopy. Cytosolic Ca2+ levels and mitochondri al membrane potential were determined by flow cytometry; adenine nucle otide concentrations by HPLC. Mitochondrial dehydrogenase activity was measured by spectrophotometric assay. Results: Oxygen radicals damage d the plasma membrane as shown by a 6-fold LDH increase in the incubat ion medium within 180 min. At the ultrastructural level, mitochondria were the most susceptible to oxidative stress. In correlation to the p ronounced mitochondrial damage, the mitochondrial dehydrogenase activi ty declined by 70%, whereas the mitochondrial membrane potential was e nhanced by 27% after 120 min. Together this may cause the 85% decrease in the ATP concentration and the corresponding increase in ADP/AMP ob served in parallel. In addition, an immediate 26% increase in cytosoli c Ca2+ was found, a change which could be inhibited by BAPTA, reducing cellular damage. Conclusion: Cytosolic Ca2+ synergizes with oxygen ra dicals causing alterations of the ultrastructure and energy metabolism of acinar cells which might contribute to the cellular changes found in early stages of acute pancreatitis.