Exchange of endogenous selenium for dietary selenium as Se-82-enriched selenite in brain, liver, kidneys and testes

Male Wistar rats were fed a diet containing selenium (Se) in the form of Se -82-enriched selenite at the adequate concentration of 0.2 mug Se/g diet, i .e. a Se-deficient diet (<0.03 <mu>g Se/g) fortified with Se-82-enriched se lenite, from 5 weeks of age for 20 days, and the systemic disposition of th e labelled Se and exchange of endogenous naturally occurring Se for the lab elled Se were monitored in four organs. Features characteristic of each org an in terms of Se metabolism were revealed by plotting the disposition of S e-82 and exchange of endogenous Se for Se-82 against the number of days of feeding Se-82-selenite. Labelled Se amounted to 83.7, 80.8, 73.2 and 41.9% of the total Se in the liver, kidneys, testes and brain, respectively, afte r feeding Se-82-selenite for 20 days, suggesting that the disposition and e xchange were most efficient in the liver but least efficient in the brain. However, when the weight gain of the four organs during the feeding period was taken into consideration, the apparent higher exchange was concluded to be caused by weight gain, i.e., more efficient uptake of the labelled Se b y proliferating cells than non-proliferating cells in the liver, kidneys an d testes. On the other hand, the uptake and exchange in non-proliferating c ells were greater in the brain than in the other organs, especially in the late observation period. The relative metabolic turnover rates of selenopro teins were shown to be easy to determine from the relative exchange rates o f endogenous Se for exogenous Se in the distribution profiles of Se obtaine d by the HPLC-ICP MS method. (C) 2000 Elsevier Science Inc. All rights rese rved.