CAT and Hyperoxaluria: The fact that oxalate and CaOx crystals appear to induce strong ROS activation, especially in the absence of any concomitant up-regulation of ROS scavengers such as SOD and catalase, suggests the renal tissues during prolonged hyperoxaluria are bathed in free radicals and molecules with unpaired electrons, including superoxide anion (O2–), hydroxyl radical (OH), and hydrogen peroxide (H2O2).