Effect of acute selenium restriction on whole body endogenous selenium and the selenite-exchangeable metabolic pool in the adult rat

Abstract

The time course of changes in whole body endogenous selenium (Se end) was investigated during a short-term (7-day) selenium restriction study in the adult rat. The method of continuous feeding with a stable isotope of selenium was used to permit normal intake of selenium while distinguishing between the dietary and endogenous components of body selenium. Additionally, the effect of short-term selenium restriction on the time course of the selenite-exchangeable metabolic pool (Se-EMP) was investigated. Two groups of adult male rats were intubated with the in vivo stable isotope 74SeO 3 2−, then fed a Torula yeast diet (selenium <0.02 μg/g) and either deionized water (−Se group) or deionized water containing selenium as 76SeO 3 2− (0.1 μg selenium/ml) (+Se group). Three animals from each group were killed at 24-hour intervals. Whole body Se end and the estimated size of Se-EMP (W Se-EMP) were determined using hydride generation-inductively coupled plasma mass spectrometry for isotopic measurements. Whole body Se end decreased linearly in the +Se group (Se° end: 54.4 μg; Se end at 3 days: 49.3 ± 2.1; Se end at 7 days: 45.2 ± 2.2). The decrease was exponential for the −Se group (Se° end: 54.4 μg; Se end at 3 days: 42.9 ± 0.3; Se end at 7 days: 42.2 ± 0.7). The value of W Se-EMP,pl (μg) was 19.8 ± 0.6 at 1 day and 19.7 ± 1.0 at 7 days for the +Se group. The corresponding values for the −Se group were 15.7 ± 1.5 and 18.8 ± 0.4. All respective values of W Se-EMP,pl for the −Se group were significantly smaller than for the +Se group ( P < 0.05), with the exception of values at days 6 and 7. The value of W Se-EMP,urine (μg) was 2.1 ± 0.2 at 1 day, increasing rapidly to 23.5 ± 1.5 at 7 days for the +Se group. The corresponding values for the −Se group were 3.0 and 23.1.