Dissociation between gene expression and protein contents of tissue superoxide dismutase in a rat model of lethal burns

The aim of this study was to examine the changes in the tissue Cu/Zn- and the Mn-SOD contents and gene expression following mild and severe burns in a rodent burn model. Thirty-eight male Wistar rats, weighing 208–278 g, were divided into a sham burn group and two burn groups, with one receiving burns to 35% of the body surface and the other to 60%. Twenty animals of the burn groups were monitored daily for 7 days after injuries to examine survival. Six animals in the sham, 35 or 60% burn group were sacrificed at 3 h postburn, and the blood, lungs and kidneys were collected for a biological analysis. The Cu/Zn- and Mn-SOD contents of the tissue and plasma specimens were measured using ELISA. The mRNA expressions of Cu/Zn- and Mn-SOD were determined by a Northern blot analysis. The survival rate of the 60% burn group for 7 days was 30%, whereas the survival rate of the 35% burn group was 100%. The mRNA expressions of Mn-SODs in the lung and the kidney were significantly higher in the 60% burn group than in 35% burn or sham burn group, as was the mRNA expression of lung Cu/Zn-SOD. Nevertheless, the tissue SOD contents in the 60% burn group (mortality 70%) did not exceed those in the 35% group. Based on these findings, tissue SOD synthesis is thus suggested to be inhibited in lethal burns in spite of a strong mRNA expression of SOD.