NETWORKING ANTIOXIDANTS IN THE ISOLATED RAT-HEART ARE SELECTIVELY DEPLETED BY ISCHEMIA-REPERFUSION

Although cardiac endogenous antioxidants have been reported to be oxid ized and decreased by ischemia-reperfusion, little is known whether th e changes in these antioxidants are correlated with each other in a sy stematic relationship. In this study, isolated rat hearts were subject ed to various periods of ischemia-reperfusion using the Langendorff me thod, and the content and/or redox status of tissue antioxidants were analyzed. Significant losses in the tissue hydrophilic antioxidants, a scorbate, and glutathione were observed. These losses were dependent o n the duration of the reperfusion period (between 0-40 min) but not of ischemia (20-60 min). Marked increases of dehydroascorbate and glutat hione disulfide, the oxidized forms of ascorbate and glutathione, resp ectively, were found during reperfusion, but these changes were not ob served during ischemia. These findings indicate that the tissue hydrop hilic antioxidants are easily oxidized and may be the first line of an tioxidant defenses during reperfusion. Lipophilic antioxidants, like u biquinol 9 and vitamin E, were not decreased during ischemia-reperfusi on using regular buffer; however, if oxidative stress was induced by a ddition of H2O2 to the buffer solution during reperfusion after 20 min of ischemia, decreases in both the hydrophilic and hydrophobic antiox idants were noticeable. With 100 mu M H2O2, the tissue antioxidant dec reases were ubiquinol 9 (39%), vitamin E (3%), glutathione (44%) and a scorbate (58%). Only with 500 mu M H2O2 treatment were marked decrease s in tissue vitamin E (65%) observed; this was associated with almost complete depletion of tissue ubiquinol 9 (95%). These results suggest that prior to the consumption of vitamin E, other antioxidants are dep leted and that vitamin E may serve as the ultimate antioxidant, protec ting the integrity of cellular membranes. Thus, in this work, cardiac antioxidants were demonstrated to change in a systematically organized relationship under ischemia-reperfusion. This graded utilization of a ntioxidants supports the redox based antioxidant network concept, foun d to be present in other biological systems. (C) 1998 Elsevier Science Inc.