Effects of Hydrogen Peroxide on Rabbit Corneal Bioelectric Properties

ABSTRACT

The rabbit cornea was studied in vitro in modified Ussing chambers to determine the effects of ion transport inhibitors and hydrogen peroxide(H2O2) on ion transport through the cornea by measuring the bioelectric properties. Apical(tear side, T side) addition of furosemide, bumetanide and SITS were ineffective on resting Isc(short circuit current). Apical addition of 1.0mM amiloride(Na+/H+ antiport inhibitor) and NPAA(Cl- channel blocker) markedly reduced the resting Isc, but basolateral(stromal side, S side) addition of amiloride was ineffective. The site of action of these agents was the apical membrane. H2O2, an oxygen free radical, markedly increased the lsc when was added to the T side, but S side addition of the H2O2 was ineffective. To determine the degree of cellular catalase participation in protection against H2O2 induced injury the cornea was pretreated with ATAZ for 30 min prior to H2O2 action. The increase of lsc by H2O2 was markedly potentiated after pretreatment with ATAZ on T side compared to that of S side addition. This result indicates that the corneal endothelial H2O2 may be largely degraded by catalase. When H2O2 was added to the T side, Isc was raised by increased ion transport. All ion transport inhibitors that were used inhibited the H2O2 effect on Isc. Moreover, amiloride and NPAA markedly inhibited induced lsc by H2O2. These results suggest that H2O2 stimulates the corneal epithelial ion transport and that its site of action is apical membrane Na+/H+ antiport system and CI- channel system.