The metabolism of (75Se)selenite in young women.

I. The long-term fate of an oral dose of ['sSe]selenite was studied in three young women. 2. Urinary and faecal excretion, respiratory and dermal losses and whole-body retention of W e 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 W e 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 W e 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.