TISSUE DISTRIBUTION OF IMMUNOREACTIVE MOUSE EXTRACELLULAR-SUPEROXIDE DISMUTASE

Protein content and mRNA expression of extracellular superoxide dismut ase (EC-SOD) were investigated in 16 mouse tissues. We developed a dou ble-antibody sandwich ELISA using the affinity-purified IgG against na tive mouse EC-SOD. EC-SOD could be detected in all of the tissues exam ined (lung, kidney, testis, brown fat, liver, adrenal gland, pancreas, colon, white fat, thymus, stomach, spleen, heart, skeletal muscle, il eum, and brain, in decreasing order of content measured as mu g/g wet tissue). Lung showed a markedly higher value of EC-SOD than other tiss ues. Interestingly, white fat had a high content of EC-SOD in terms of micrograms per milligram protein, which corresponded to that of lung. Kidney showed the strongest expression of EC-SOD mRNA. Relatively str ong expression of the mRNA was observed in lung, white fat, adrenal gl and, brown fat, and testis. Heart and brain showed only weak signals, and no such expression could be detected in either digestive organs or skeletal muscle. Immunohistochemically, EC-SOD was localized mainly t o connective tissues and vascular walls in the tissues examined. Deep staining in the cytosol was observed in the cortical tubular cells of kidney. These results suggest that EC-SOD is distributed systemically in mice and that the physiological importance of this enzyme may be a compensatory adaptation to oxidative stress, particularly in lung and kidney.