Stability of glutathione peroxidase in ovine blood samples under various storage conditions and the response of this enzyme to different methods of selenium supplementation

Abstract

Levels of the selenium-containing enzyme glutathione peroxidase (GSH-Px) in haemolysates of ovine whole blood and in washed erythrocytes were almost identical, indicating that plasma has no significant effect on the method used. Blood containing sodium heparin, sodium EDTA or fluoride/oxalate as anticoagulant could be stored at 4° or 20° for at least a week without appreciable loss of GSH-Px activity. At 27°, storage time should not exceed 4 days. Irrespective of the anticoagulant used, GSH-Px levels in haemolysates prepared on the day of blood collection and stored at 4° remain unchanged over 7 days. At 20° or 27° storage times should be limited to 2-3 days in the case of blood containing sodium heparin or sodium EDTA and to 2 or 1 day at 20° or 27° respectively in the case of fluoride/oxalated blood. In sheep treated orally or subcutaneously with sodium selenite or sodium selenate, maximum levels of GSH-Px in the blood were reached in approximately 30 days. Thereafter the GSH-Px levels fell only slowly throughout the 108 day experimental period. Using the analytical method described, GSH-Px levels in ovine blood of ≤ 20 μmoles NADPH oxidised min^-1.g Hb^-1. indicate a selenium deficiency.