The effects of the restriction of food and water intakes on gastrointestinal absorption, distribution to organs and excretion of
131I were investigated in C3H/He mice. The animals were divided into four groups and administered orally 37 kBq carrier-free Na
131I in 0.25 ml normal saline. One group of animals was given food and water
ad libitum throughout the experimental period. Food and water to the remaining groups were restricted before and/or after the administration of
131I. The animals in each group were sacrificed 4 h and 24 h after administration, and the activity of
131I in thyroid, blood, liver, kidney, gastrointestinal tract, urine, feces, and carcass was measured. There was a significant increase in the retention of
131I in the thyroid and the concentration of
131I in the blood due to the restriction of food and water after the administration of
131I. In contrast, a significant decrease in the urinary excretion was observed in these animals. In those animals, which fasted before administration only, the retention of
131I in the thyroid and other organs were decreased. Therefore, for an accurate diagnosis and effective therapy with radioiodine as well as effective radiation protection, the intake of food and water should be taken into account.
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