Selenium Metabolism

Young male rats injected with subtoxic amounts of sodium selenite exhaled as much as 40% of the injected selenium within 10 hours when maintained with a crude diet; elimination of selenium by this route was usually about double that by rats fed a purified diet. Rats receiving the crude diet retained less selenium in the tissues; excretion via the urine and the gastrointestinal tract was similar when feeding either of the two diets. Arsenite markedly increased the excretion of selenium into the gastrointestinal tract, this excretion amounting to 30 to 40% of the injected dose in most animals, compared with 5 to 15% in the absence of arsenite. Levels of selenium in the blood, liver, and carcass were decreased by arsenite, as were the amounts in the expired air; kidney levels were increased. Urinary excretion of selenium was not affected by arsenite. The amounts of selenium in the blood, liver, and carcass increased in the presence of cadmium, kidney selenium decreased, and excretion via the gastrointestinal tract, the urine, and the expired air decreased.