COMPARISON OF METHYLATED SELENIUM METABOLITES IN RATS AFTER ORAL-ADMINISTRATION OF VARIOUS SELENIUM-COMPOUNDS

To identify the metabolic pathway of selenomethionine (Se-Met), the be haviors 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 co mpared. 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 re cognized in these two organs of the group of rats given Se-Met. Althou gh the cumulative total Se content excreted into the urine for 48 h af ter administration of Se-Met was highest, almost no difference could b e detected among the urinary trimethylselenonium ion (TMSe) contents i n these three administration groups. However, the total Se and TMSe co ntents excreted in the urine of rats in these groups for 12 h after ad ministration of Se-Met were both twice those given Se-Cys or Na2SeO3. Furthermore, the amount of production oi TMSe in the liver was rapidly elevated for 30 min after administration of Se-Met. In contrast, in t he liver of rats given Se-Cys of Na2SeO3 TMSe was produced slowly. The findings that the TMSe formation in the liver of the group of rats gi ven Se-Met occurs earlier than that in the group oi rats given Se-Cys or Na2SeO3 suggested that Se-Met may be directly and enzymatically cat abolized to produce methylselenol, which is easily methylated to TMSe.