Selenium metabolism and excretion in mice after injection of 82Se-enriched selenomethionine

Abstract

The organic Se compounds (particularly selenomethionine [SeMet]) in plants and yeasts are very effective chemoprotectants for mammalian cancer. To characterize the dynamics of selenomethionine utilization pathways, we intravenously injected (82)Se-enriched SeMet into mice under different nutritional states (Se-adequate and Se-deficient mice) and then measured their endogenous and exogenous (82)Se levels. Furthermore, we quantified Se compounds and selenoproteins in liver, kidneys, plasma, and urine. The average recoveries of exogenous (82)Se from solid tissues, urine, and feces were 81% for Se-adequate mice and 84% for Se-deficient mice. Exogenous (82)Se was distributed in the hepatic and renal cytosols as cellular glutathione peroxidase (cGPx), selenosugar, and SeMet within 1 h after injection. Synthesis of cGPx was maintained until 72 h after injection, regardless of the Se nutritional status. Whereas plasma levels of exogenous (82)Se as selenoprotein P (Sel-P) peaked at 6 h after injection, those of Se-containing albumin (SeAlb), extracellular GPx, and SeMet peaked at 1 h after injection. These results suggest three Se transport pathways in mice injected with SeMet: SeAlb (within 1 h after injection); SeMet (from 1 to 72 h after injection); and Sel-P (from 6 to 72 h after injection). The amount of Sel-P in Se-deficient mice was 1.5 times that of Se-adequate mice, and this increase was much larger than Se-containing compounds other than Sel-P. Our results indicate that Sel-P has an important role in Se transport when the nutritional supply of Se is insufficient.

Synthesis of [77Se]-methylselenocysteine when preparing sauerkraut in the presence of [77Se]-selenite. Metabolic transformation of [77Se]-methylselenocysteine in Wistar rats determined by LC–IDA–ICP–MS

“…The detection of low amounts of MeSeCys in liver and kidney in its intact form after feeding animals with such species has been reported by other authors [31,32]. Suzuki et al [31] evaluated the metabolisms of 77 SeMet and Me 76 SeCys orally administrated in [31], since the presence of SeCys, released from selenoproteins, in these metabolically active glandular visceral tissues (heart, kidney, liver, brain and) can be explained as a result of the conversion of the species initially present in the supplemented diet..…”

Kynurenine aminotransferase 3/glutamine transaminase L/cysteine conjugate beta-lyase 2 is a major glutamine transaminase in the mouse kidney

“…In pigs, selenium concentration was generally the highest in the kidney after administration of selenomethionine [39] . However, in the mouse, the liver absorbed the injected selenomethionine more efficiently than did any other tissues, showing the highest selenium concentrations [40] . Regarding the fact that selenomethionine is a relatively good substrate of the mouse KAT3/GTL, and possibly rat and human KAT3/GTL enzymes, the differences of tissue preference of selenomethionine between different animals (higher concentration in the kidneys of the pig and rat, higher concentration in the liver of the mouse) may explain the different tissue localization of KAT3/GTL between mice and the others (rats and pigs), although the mechanism is not yet understood.…”

XAS studies of Se speciation in selenite-fed rats

“…19-21 The EXAFS spectra of the liver and kidney of rats fed the high Se diet indicate the presence of Se–Se–Se and/or diselenide species in both spectra, as well as the presence of Se–S species in the kidney. We recognise that the total value of N = 3 (two Se–Se bonds and one Se–S bond) is chemically unlikely (the trimethylselenonium ion (SeMe + 3 ) has a coordination number of three, but neither XANES nor PCA identifies it as a likely component).…”