Oxidative inhibition of Ca²⁺-ATPase in the rabbit lens

Hydrogen peroxide inhibition of maximum Ca²⁺-ATPase and Na⁺,K⁺-ATPase activity was measured in a membrane-enriched preparation of rabbit lens cortical fibers and epithelium. At 5 x 10^-6 M hydrogen peroxide maximum Ca²⁺-ATPase activity was inhibited by 39%, while maximum Na⁺,K⁺-ATPase activity was stimulated. Ca²⁺-ATPase activity was almost completely inhibited at 5 x 10^-4 M hydrogen peroxide, in comparison to Na⁺,K⁺-ATPase activity, which was only inhibited by 28% at a concentration of hydrogen peroxide an order of magnitude larger. The addition of catalase to hydrogen peroxide-pretreated samples did not reverse the inhibition of Ca²⁺-ATPase by hydrogen peroxide.