Hyperoxia elevates Cu,Zn-superoxide dismutase of endothelial cells as detected by a sensitive ELISA

An enzyme-linked immunosorbent assay (ELISA) was developed for the measurement of bovine Cu,Zn-SOD. Accuracy of the ELISA and specificity of the antibody for cell-free extracts was established by: (1) measurement of antigen levels of bovine endothelial cell extracts reconstituted with pure antigen, and (2) immunoblotting with affinity purified antibody. The ELISA was highly sensitive and 0.05-0.10 ng of pure antigen could be accurately detected, which allowed the measurement of Cu,Zn-SOD in as few as 250 endothelial cells. With utilization of the ELISA for detection, DEAE-cellulose chromatography patterns of endothelial cell Cu,Zn-SOD overlapped those of pure bovine erythrocyte Cu,Zn-SOD. Exposure of cells in culture to 80% O2 for 48 h increased the relative abundance of the Cu,Zn-SOD as measured by the ELISA by 1.8-fold. Thus, endothelial cells in culture respond to hyperoxia by enhanced production of Cu,Zn-SOD protein. The ELISA developed in this study may be useful for assessing other factors that regulate cellular production of Cu,Zn-SOD.