Abstract
Distribution and retention of tritium in various tissue of a rat after administration of tritiated water (HTO) was investigated during about 100 days. Tritium incorporated into the body was rapidly and uniformly distribution in the whole body and excreted immediately with a biological half-life of 3.5 days for almost all the tissues. However, excretion of tritium incorporated into the tissue constituents was relatively slow and the retention curves were considerably different from tissue to tissue. At the end of this experiment, the highest concentration of total tritium was observed in the fat tissue, followed by brain and muscle. These results suggested that the intake of tritium from HTO into organic compounds and the excretion of tissue-bound tritium would be related to metabolic activity of the tissue. This prediction was reinforced by the experiment on age dependence.
The radiation dose to each tissue after the administration of 6.0 μCi/g body weight of HTO ranged from 2.0 to 9.5 rem, which was the highest in blood and the lowest in fat tissue. Contribution from tissue-bound tritium was within 10% of the dose from total tritium for each tissue, except for fat tissue which was 64%.
