SELENIUM DEFICIENCY SUPPRESSES THE S-GLUTATHIOLATION OF CARBONIC ANHYDRASE-III IN RAT HEPATOCYTES UNDER OXIDATIVE STRESS

To examine the modification of reactive sulfhydryls of carbonic anhydr ase III (CA III), hepatocytes were prepared by collagenase perfusion f rom Sedeficient and Se-adequate male Sprague-Dawley rats. After 24 h i n culture, hepatocytes were treated for 15-30 min with one of two oxid ative stressors, t-butyl hydroperoxide (t-BuOOH) or menadione. Modific ation of CA Ill was measured by isoelectric focusing/immunoblotting. F ormation of glutathione disulfide (GSSG) during oxidative stress was m arkedly less in hepatocytes of Se-deficient rats than in those of Se-a dequate rats. During treatment with t-BuOOH, GSSG formation in hepatoc ytes from Se-adequate rats reached a maximum at 3 min, and then GSSG w as gradually reduced to glutathione. After menadione treatment, intrac ellular GSSG irreversibly increased in hepatocytes of Se-adequate rats but not in those of Se-deficient rats. A modification of CA III that was reversible by dithiothreitol treatment concurred with the formatio n of GSSG during treatment with either t-BuOOH or menadione. Although modification of CA III occurred in hepatocytes from Sedeficient rats, the extent of modification was significantly less than in Se adequacy, and the modification was less reversible by dithiothreitol than in he patocytes from Se-adequate rats. Selenium deficiency may be useful in examining the importance of modification of specific proteins subjecte d to oxidative stress.