Distribution and metabolism of selenohomolanthionine labeled with a stable isotope

The distribution and metabolism of selenohomolanthionine (4,4'-selenobis[2-aminobutanoic acid], SeHLan), a newly identified selenoamino acid in selenized Japanese pungent radish, were evaluated by administering ⁷⁷Se-labeled SeHLan at a dose of 25 μg/kg body weight in rats. Exogenous ⁷⁷Se of SeHLan was preferably distributed to the kidneys and remained in the intact form for up to 6 h after dosing. The accumulation in the kidneys is one of the specific characteristics of SeHLan, differing from other selenoamino acids, such as selenomethionine and Se-methylselenocysteine, which preferably accumulate in the pancreas. The intact form of SeHLan was detected in the serum and kidney supernatant but not in the urine, suggesting that the amount of exogenous Se that was distributed to the kidneys was within metabolic capacity. Indeed, the exogenous Se was converted into two urinary metabolites, Se-methylseleno-N-acetyl-galactosamine and trimethylselenonium. Exogenous Se was also detected in several selenoproteins, including selenoprotein P and extracellular glutathione peroxidase. SeHLan is expected to be a potential supplemental source of Se because its distribution differs from that of selenomethionine and Se-methylselenocysteine.