Blood selenium and glutathione peroxidase activity in pregnant women: comparative assays in primates and other animals.

The influence of pregnancy on blood selenium levels and glutathione peroxidase (GSH-Px) activity was studied in women. Whole blood and plasma selenium levels decreased whereas erythrocyte and plasma GSH-Px activities increased with the progress of pregnancy. The ratio of erythrocyte GSH-Px activity to whole blood selenium levels was 4- to 5-fold higher in rats and sheep than in primates (humans and monkeys), suggesting that more selenium is associated with GSH-Px in erythrocytes from rats and sheep than from primates. In assays of blood with low GSH-Px activity such as that from humans or selenium-deficient animals, a component of the erythrocyte other than GSH-Px was found to contribute more to the peroxidase activity. Evidence was obtained to indicate that t-butyl hydroperoxide is a better substrate than hydrogen peroxide for the assay of low GSH-Px erythrocyte activity. The length of time that the blood was stored before assay was found to have an effect on erythrocyte GSH-Px activity, and the storage patterns may be dependent on the species of animal from which the blood is drawn.