Speciation and metabolism of selenium injected with (82) Se-enriched selenite and selenate in rats

Selenate and selenite injected intravenously into rats were speciated by th e HPLC-ICP MS method with use of an enriched stable isotope as the tracer. In dose-relation experiments, Se-82-enriched selenate or selenite was injec ted intravenously into male Wistar rats of 8 weeks of age (three rats/group ) at single doses of 10, 25, 50, 100 and 200 mug/kg body weight for the sel enate group, and 2, 5, 10, 25 and 50 mug/kg body weight for the selenite gr oup. The animals were sacrificed 1 or 24 h later, and the concentrations an d distributions of Se-82 in the liver, kidneys, serum, and urine remaining in the bladder or 24-h urine were determined. In time-course experiments, S e-82-enriched selenate and selenite were injected at doses of 50 and 10 mug /kg body weight, respectively, and the animals were sacrificed 5, 15, 30, 6 0 and 180 min later. It was suggested that selenate is directly taken up by the liver with an efficiency of approximately 1/2 compared with selenite, the latter being taken up by the liver after being metabolized to selenide in red blood cells. Although selenate and selenite were metabolized differe ntly in the bloodstream, and also a part of only selenate was excreted dire ctly into the urine, the Se-82 taken up by the liver was shown to be metabo lized in a manner indistinguishable between selenate and selenite. Se-82 of selenite origin but not of selenate origin was suggested to undergo redox reaction in the bloodstream. These results suggest that although parenteral selenate is utilized less efficiently by the body, it is utilized in the l iver in a similar manner to selenite much more safely. (C) 2001 Elsevier Sc ience B.V. All rights reserved.