摘要：Absorption, elimination, and distribution of radioactive selenium were examined after a long term repeated oral administration of sodium 75Se-selenite (0.03mg/kg/day) in male rats. Oral administration of the compound and measurement of radioactivities in the whole body of living animals, in feces and urine just before each dosing, were continued every day for approximately 90 days, using a Packard ARMAC scintillation counter. Whole body count of 75Se increased rapidly during the initial 10 days and thereafter continued to increase rather slowly and linearly. It was observed that radioactivity was excreted mainly via urine and a small amount in feces. After the termination of repeatad administration of sodium 75Se-selenite for 90 days, elimination of 75Se was rather rapid for 10 days, and later, it continued slowly and the whole body count decreased along an exponential line. Therefore, linear retention line of selenium was depicted graphically on a semilogarithmic scale. Biological half-life of absorbed labeled selenium in the whole body, calculated from this line, was 26.4 days. Biological half-life of 75Se in each organ and tissue was also calculated as follows : sodium 75Se-selenite (0.03mg/kg/day) solution was given to a number of rats by repeated daily administration for 15 days, and the distribution pattern was observed at 4, 22, 39 and 65 days after the termination of administration, measuring the γ-radio-activities in 17 kinds of organs and tissues with well-type scintillation counter. The values obtained for were 36 days for hair, 29.9 days, for thyroid, 26.9 days, for pituitary, all longer than the value in the whole body. By the repeated administration of sodium 75Se-selenite for 35 and 90 days, remarkable accumulation of 75Se was found in the epididymis, kidney, liver, and testis, but the content of 75Se in the liver and testis decreased significantly 65 days after the termination of administration.
