Antioxidant‐oxidant balance in the glomerulus and proximal tubule of the rat kidney

Abstract

1. Antioxidant and oxidative enzymes were examined in renal glomeruli and proximal tubules of healthy young rats (10-12 weeks old), and results were related to the superoxide anion generation of these tissues. 2. Activities of superoxide dismutases, catalase, and glutathione peroxidase were 3- to 6-fold higher in proximal tubules than in glomeruli. Similarly, enzyme levels and mRNA levels of superoxide dismutases and catalase were significantly higher in proximal tubules. 3. NADH- and NADPH-dependent oxidase activity and xanthine oxidase activity were not different in glomeruli and proximal tubules. 4. Measurements with lucigenin-enhanced chemiluminescence in vital tissues indicated 10-fold higher rates of superoxide anion in glomeruli than in tubules. 5. Compared with the young rats, tubules of 8-month-old rats had significantly higher superoxide anion rates and lower superoxide dismutase activity, whereas NADH- and NADPH-dependent oxidase activities were unchanged. 6. We conclude that considerable differences in the antioxidant-oxidant balance exist between the glomerulus and proximal tubule. Results from experiments using chemiluminescence in vital tissues suggest that changes in the antioxidant-oxidant balance have an effect on oxygen radical levels. The relevance of the observed differences to glomerular and tubulo-interstitial disease remains to be determined, but a greater susceptibility of the glomerulus to oxidant stress might be anticipated.