Metabolic studies of [75Se]selenomethionine and [75Se]selenite in the rat

Abstract

1. Information was sought concerning the long-term fate of orally and intravenously administered [⁷⁵Se]selenomethionine and [⁷⁵Se]selenite in rats.2. Urinary and faecal radioactivity was assayed during the 1st week and whole-body radio-activity was determined weekly for 16 weeks. Rats were killed at intervals for analysis of ⁷⁵Se tissue distribution.3. Intestinal absorption after oral administration was estimated to be 91–93% for selenite and 95–97% for selenomethionine.4. Urinary excretion of absorbed [⁷⁵Se]selenite was greater than that of [⁷⁵Se]selenomethionine during the 1st week.5. After the 1st week, whole-body retention diminished exponentially at a similar rate in rats given either selenomethionine or selenite. Except for the erythrocytes, ⁷⁵Se content of individual tissues also decreased exponentially.6. It appears that, after an initial period, ⁷⁵Se from either selenomethionine or selenite is metabolized similarly, suggesting that Se from both potential dietary sources is ultimately incorporated into the same metabolic pool.