Effects of dietary selenium species on Se concentrations in hair, blood, and urine

The effects of the chemical species and concentration of selenium (Se) in diets on the concentrations of Se in hair, blood serum, red blood cells (RBCs), and urine were studied to gain an insight into the toxicological and nutritional significance of different chemical forms of Se. Male Wistar rats were fed an Se-deficient diet (Se, less than 0.03 microgram/g) for 3 weeks, and then an Se-adequate (Se, 0.2 microgram/g) or Se-excess diet (Se, 2.0 micrograms/g), including seleno-L-methionine (SeMet) or selenite for up to 12 weeks. Hair, blood, and urine specimens were obtained every two weeks, and the concentrations of Se and its distribution in serum and urine on a size-exclusion column were determined. The concentrations of Se in hair, serum, and urine attained constant levels 2 weeks after a change of in the dietary Se concentration irrespective of the chemical species, the levels being dependent on the chemical species and the concentration. Specifically, in hair and serum, selenite gave the lowest constant levels irrespective of the dose, while SeMet resulted in higher levels than selenite in a dose-dependent manner. The two major selenoproteins in serum exhibited comparable concentrations. On the other hand, in urine, the concentration of Se was dependent on the dose but not on the chemical species. The results could be explained by regulated metabolism of selenite, and both nonregulated and regulated aspects of the metabolism of SeMet.