Comparison of Methylated Selenium Metabolites in Rats after Oral Administration of Various Selenium Compounds.

Abstract

To identify the metabolic pathway of selenomethionine (Se-Met), the behaviors of methylated metabolites in male Sprague-Dawley rats (6 weeks of age) treated orally with a single dosage (1 mg Se/kg body weight) of Se-Met, selenocystine (Se-Cys) or sodium selenite (Na2SeO3) were compared. The total Se contents in the kidney and in the liver from rats treated with these three Se compounds were both markedly higher than those in other organs. The highest accumulation of the total Se was recognized in these two organs of the group of rats given Se-Met. Although the cumulative total Se content excreted into the urine for 48 h after administration of Se-Met was highest, almost no difference could be detected among the urinary trimethylselenonium ion (TMSe) contents in these three administration groups. However, the total Se and TMSe contents excreted in the urine of rats in these groups for 12 h after administration of Se-Met were both twice those given Se-Cys or Na2SeO3. Furthermore, the amount of production of TMSe in the liver was rapidly elevated for 30 min after administration of Se-Met. In contrast, in the liver of rats given Se-Cys or Na2SeO3 TMSe was produced slowly. The findings that the TMSe formation in the liver of the group of rats given Se-Met occurs earlier than that in the group of rats given Se-Cys or Na2SeO3 suggested that Se-Met may be directly and enzymatically catabolized to produce methylselenol, which is easily methylated to TMSe.