Effect of Chronic Selenite Supplementation on Selenium Excretion and Organ Accumulation in Rats

Abstract

We examined the effect of chronic selenite supplementation on whole body and selected organ selenium (Se) accumulation, urine excretion of total Se and trimethylselenonium ion, and Se balance in adult male rats. Animals were housed in metabolic cages and given either deionized water or water containing 4 micrograms of Se/mL as selenite for 30 d. Absorption of selenite was nearly complete, with only approximately 10% of ingested Se appearing in feces. There was a rapid rise in urinary Se that reached a plateau within a few days and accounted for 54 +/- 2% of the intake. Excretion of trimethylselenonium ion (TMSe) in urine increased rapidly, representing 35-40% of urinary Se in the supplemented animals compared with only 2% for the control group. In one experiment, rats were killed at 30 d and total carcass Se was measured using isotope dilution analysis. Supplemented rats had only a modest increase in whole body Se (94 +/- 4 micrograms Se vs. 66 +/- 3 in controls). Calculation of Se balance in the supplemented rats showed that approximately 35% of ingested Se could not be accounted for by urine plus fecal losses combined with the portion retained in the carcass. The results from this study demonstrate that under the condition of supplementation at 4 micrograms of Se/mL of drinking water, pathways other than urinary and fecal excretion may account for a substantial portion of Se loss.

Homeostatic adjustments of selenium metabolism and tissue selenium to widely varying selenium supply in 75Se labeled rats

“…Gaseous exhalations of Se are discussed as an additional excretion pathway of Se (G anther et al 1966; J anghorbani et al 1990). However, Se exhalations were not of quantitative importance in the present experiment since the injected 75 Se was recovered completely irrespective of the level of Se supply.…”

Selenious acid as a source of selenium added for nutritional purposes to food supplements

“…In animal studies, approximately 90% absorption of selenite by male Sprague Dawley rats was reported, with only 10% of the ingested selenium being detected in the faeces (Janghorbani et al, 1990). A similar degree of absorption was reported in mice and dogs.…”

XAS studies of Se speciation in selenite-fed rats

“…Selenium status is known to change with age, in particular, a decline in selenium status has been documented in the elderly, 49,50 and rats appear to adapt in response to long-term selenium supplementation. 46,51 The interest in long-term selenium supplementation as a chemoprevention measure, 52 or short to medium-term treatment with selenium as an adjuvant therapy, 53,54 requires more investigations of the changes of selenium status and speciation with age and duration of selenium supplementation.…”