Distribution of selenium and glutathione peroxidase in the rat

The selenium content was determined in the adrenals, brain, erythrocytes, femur, hair, heart, kidneys, lungs, muscle, pancreas, plasma, spleen, testes, and thymus of rats, which had been fed a commercial rat diet containing 0.3 mg Se/kg diet. In the plasma, the erythrocytes, and the soluble fraction of the tissues (with the exception of femur and hair) the activity of the glutathione peroxidase (GSH-Px) was measured, using both hydrogen peroxide and t-butyl hydroperoxide as substrates. From the masses of the tissues and the values for the selenium content and the GSH-Px activity, the distribution of the element and the enzyme in the body was calculated. For selenium the main pools were the muscle and the liver, and for the GSH-Px, the liver and the erythrocytes. By comparing the selenium content and the GSH-Px activity the percentage of the tissue selenium, which was bound to the enzyme in the soluble tissue fraction, was estimated. This percentage differed considerably from tissue to tissue, the highest value being found in the erythrocytes and the smallest in the testes. According to this estimation the majority of the selenium in the rat is not contained in the GSH-Px but in other compounds.