RESUMO
The properties of Cu,Zn-superoxide dismutase (SOD) from rat liver after 2-hour total ischemia or after ischemia with subsequent 24-hour reperfusion were studied. Two hours after ischemia the specific activity of SOD decreases drastically (about 3-fold) - from 510 +/- 11 u./mg in normal tissue and 196 +/- 33 u./mg after ischemia showing a further increase after reperfusion (276 +/- 40 u./mg). Using competitive immunoenzymatic analysis, the relative contents of SOD in the cytosol were determined. After ischemia the SOD content in the cytosolic fraction decreased (approximately 3-fold) but returned to the initial level after reperfusion. Polyacrylamide gel electrophoresis revealed that in control samples active SOD is heterogeneous and produces 3-4 bands, similar to the purified SOD from rat liver. After the ischemia the intensity of minor fast band IV increased and a new band V of a still higher mobility appeared. After the reperfusion the electrophoretic patterns were similar to control. Two or three times more SOD antigen from ischemia liver cytosol was absorbed to the surface of polystyrol plate in a direct sorption enzyme immunoassay procedure as compared to that from intact liver cytosol. It is suggested that the decreases of amount and the activity as well as changes of properties of SOD could be due to its oxidative modification and degradation of the modified enzyme.
