Oxidative stress generated during islet isolation and transplantation causes islet cell damage. These oxidative injuries are mediated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). MCI-186 is an antioxidant used for clinical treatment of cerebral infarction in Japan. We examined a possible protective effect of MCI-186 on islet cells against oxidative stress. Islets isolated from Sprague-Dawley rats by collagenase P digestion were purified by density gradient centrifugation with Ficoll. Islets were treated with hydrogen peroxide (H(2)O(2); 5 to 250 micromol) in the presence or absence of MCI-186. Cell death was measured by an LDH release assay. Maximum islet cell death was observed at 250 micromol of H(2)O(2). MCI-186 inhibited islet cell death in a dose-dependent manner with significant reduction above 30 micromol. From the results observed we suggest that the antioxidant effects of MCI-186 may prove beneficial to improve the preservation of islet cells.