The metabolism of [75Se]selenite in young women

The long-term fate of an oral dose of [75Se]selenite was studied in three young women. 2. Urinary and faecal excretion, respiratory and dermal losses and whole-body retention of 75Se were measured, and also 75Se turnover in whole body, blood and tissues during a period of 16–20 weeks. 3. Intestinal absorption of [75Se]selenite by the three subjects was 70, 64 and 44% of the dose. 4. Urinary excretion accounted for 14–20% of absorbed 75Se in the 1st week. There were only trace amounts of radioactivity in expired air and no dermal loss was detected. 5. After an initial phase in which radioactivity decreased rapidly, whole-body retention of 75Se diminished exponentially with a half-time of 96–144 d. Radioactivity in the liver, heart and plasma decreased more rapidly than that in the whole body, but radioactivity in skeletal muscle and bone decreased more slowly.