Comparative Utilization of Fish Selenium and Inorganic Selenite by Rats of Normal Selenium Status

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Abstract
Rats of a normal Se status were fed diets based on fish (rainbow trout) as the main protein source. A 4-wk experiment with 3 dietary groups (low fish Se, high fish Se and selenite supplementation) was performed, and the Se absorption, excretion and retention were recorded. Samples of blood serum, liver, kidneys, testes, hair, spleen, lungs, heart, bain and skeletal muscle were collected for analysis of Se. Glutathione peroxidase activity was measured in the blood serum. A Se supplementation of approximately 1 mg/kg (high fish Se and selenite group) yielded a Se retention of only 7% of the intake, while in the group with a dietary Se concentration of .apprx. 0.1 mg/kg (low fish Se group) the Se retention was 50%, resulting in almost the same absolute Se retention in all 3 groups. The liver and kidneys showed the highest accumulations of Se, reflecting the participation of these organs in the excretion of surplus Se. The highest relative uptake of Se was recorded in the testes, which increased equally in all dietary groups. The Se concentration in the other tissues investigated, as well as the glutathione peroxidase activity in the blood serum responded little to the Se supplementations. These results showed that the Se levels normally found in fish were sufficient to satisfy the need for this element in rats of a good Se status, and that inorganic selenite was absorbed and excreted at a high rate already after 1 wk.