Altered oxidative metabolism in selenium-deficient rat granulocytes

Rats fed a selenium-deficient diet for 12 to 15 wk became selenium-depleted, measured by the selenium content of liver and granulocytes. The activity of granulocyte glutathione peroxidase, a selenoenzyme, in deficient rats was 11% of the activity in replete rat granulocytes. When stimulated with an H₂O₂ generating system, the HMPS activity of the deficient granulocytes was 50% of replete; however, when stimulated with methylene blue, the HMPS activity in deficient and replete granulocytes was the same. When granulocytes were incubated with PMA or OPZ, deficient granulocytes initially had the same O₂^--generating activity as replete granulocytes; however, with increasing duration of stimulation, granulocytes from deficient rats generated less O₂^- than replete rats. After 20 min in an H₂O₂-generating system, deficient granulocytes stimulated with PMA or OPZ generated less O₂^- than replete granulocytes. These results indicate that deficient granulocytes did not metabolize H₂O₂ as well as replete granulocytes and that H₂O₂ caused damage to the O₂^- generating system. Measurement of O₂^- generation in membrane enriched particles showed the above effects were due to inactivation of the NADPH-dependent O₂^- generating system. Deficient granulocytes stimulated with OPZ for 20 min had 70% less membrane O₂^--generating activity than controls. In addition, when membrane-enriched particles were made from cells that had been stressed with an H₂O₂-generating system, NADPH-dependent O₂^--generating activity in deficient granulocytes was 50% of replete. In selenium-deficient granulocytes with low GSH-Px activity, prolonged incubation with stimulants and prior incubations with an H₂O₂-generating system caused loss of activity of the membrane-bound, NADPH-dependent, O₂^--generating system.