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 anhydrase III (CA III), hepatocytes were prepared by collagenase perfusion from Se deficient and Se-adequate male Sprague-Dawley rats. After 24 h in culture, hepatocytes were treated for 15-30 min with one of two oxidative stressors, t-butyl hydroperoxide (t-BuOOH) or menadione. Modification of CA III was measured by isoelectric focusing/immunoblotting. Formation of glutathione disulfide (GSSG) during oxidative stress was markedly less in hepatocytes of Se-deficient rats than in those of Se-adequate rats. During treatment with t-BuOOH, GSSG formation in hepatocytes from Se-adequate rats reached a maximum at 3 min, and then GSSG was gradually reduced to glutathione. After menadione treatment, intracellular 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 formation of GSSG during treatment with either t-BuOOH or menadione. Although modification of CA III occurred in hepatocytes from Se-deficient rats, the extent of modification was significantly less than in Se adequacy, and the modification was less reversible by dithiothreitol than in hepatocytes from Se-adequate rats. Selenium deficiency may be useful in examining the importance of modification of specific proteins subjected to oxidative stress.