Hydrogen peroxide effects on ionic and non-ionic permeability of the rabbit corneal endothelium.

Perfusion of the isolated rabbit corneal endothelium with 0.3 mM hydrogen peroxide (H2O2) caused an increased passive permeability to bicarbonate relative to control tissues. This was accompanied by a reduction in the active flux that resulted in a reduced net bicarbonate flux. Perfusion with 0.3 mM H2O2 resulted in a marked increase in the active and net flux of sodium beginning at two hours. By four hours the net sodium flux had increased by nine-fold over control values. Perfusion with 0.3 mM H2O2 resulted in a 16% and 30% increase in endothelial permeability to inulin and dextran, respectively. Suppression of catalase activity by in vivo pretreatment with intravenous 3-aminotriazole (3AT) did not result in an increased sensitivity of the corneal endothelium to 0.2 mM H2O2: both bicarbonate and sodium fluxes were normal. Inhibition of glutathione synthesis with intravitreal buthionine sulfoximine (BSO) increased the sensitivity of the corneal endothelium to 0.2 mM H2O2 only in the case of sodium flux, with a 4.8-fold increase in net sodium flux at 3 hours after initiation of perfusion. Bicarbonate fluxes were unaffected after BSO pretreatment. The data show that ionic and non-ionic fluxes are altered by H2O2, that pretreatment with 3AT has a minimal effect on ion fluxes while BSO markedly alters sodium flux without changing bicarbonate fluxes, and that sodium and bicarbonate movement are not locked in a symport.