ANTIOXIDANT-OXIDANT BALANCE IN THE GLOMERULUS AND PROXIMAL TUBULE OF THE RAT-KIDNEY

1. Antioxidant and oxidative enzymes were examined in renal glomeruli and proximal tubules of healthy young rats (10-12 weeks old), and resu lts were related to the superoxide anion generation of these tissues. 2. Activities of superoxide dismutases, catalase, and glutathione pero xidase 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 NADPK-dependent oxidase activity and xanthine oxidase activity were no t different in glomeruli and proximal tubules. 4. Measurements with lu cigenin-enhanced chemiluminescence in vital tissues indicated 10-fold higher rates of superoxide anion in glomeruli than in tubules. 5. Comp ared with the young rats, tubules of 8-month-old rats had significantl y higher superoxide anion rates and lower superoxide dismutase activit y, whereas NADH- and NADPH-dependent oxidase activities were unchanged . 6. We conclude that considerable differences in the antioxidant-oxid ant 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 r adical levels. The relevance of the observed differences to glomerular and tubulointerstitial disease remains to be determined, but a greate r susceptibility of the glomerulus to oxidant stress might be anticipa ted.