Superoxide augmentation in a rat brain under hyperoxia as monitored in vivo by a superoxide dismutase/catalase-modified microelectrode

It is thought that superoxide plays a role in many diseases. The concept has been supported by indirect evidences of superoxide generation. However, efforts to prove the theory by direct in vivo measurement of superoxide has been difficult because of the short life of superoxide in biological systems. To overcome this, we fabricated an Au-disk microelectrode (50 μm diameter) modified with superoxide dismutase (SOD) and catalase (CAT). The electrode responded to superoxide via hydrogen peroxide converted by SOD, and not to hydrogen peroxide from the extra-electrode matrix because it was readily eliminated by CAT. Using our electrode, we found a significant increase in the superoxide level in the striatum of freely moving rats when they were exposed to pure oxygen. We think that our electrode is a useful instrument for clarifying the pathogenesis of those diseases caused by excessive superoxide production.