A solution of
54MnCl
2 (71μCi/0.32mg MnCl
2/2ml/kg) was injected intravenously to 7 groups of 5 male rats, and the distribution of
54Mn was investigated by the measurement of radioactivities in the organs and tissues at 3 hours, 3, 7, 14, 28, 56, 113 days after dosing. Using some of the above mentioned groups of rats, the retention and excretion of
54Mn were also observed.
A major part of injected
54Mn was excreted rather rapidly in a few days after injection, and 25.3% of dose was retained at 3 days after jnjection. Thereafter, however, the gradual excretion from whole body continued and 1.8% of dose was still remained at 113 days after dosing. The biological half life (BHL) of
54Mn in the whole body was estimated as 31.6 days.
At earlier stage after dosing, thicker distribution was found in pancreas, liver, kidney, salivary gland, adrenal and pituitary, but the radioactive concentrations in these organs were decreased rather rapidly. Reversely, cerebrum, cerebellum, medulla oblongata and spinal cord showed their highest accumulation at 3-14 days after dosing, and BHL of
54Mn in these tissues and bone were significantly longer than that in whole body, resulting thicker retention at 113 days after dosing. The fact suggested the possibility of high accumulation of the metal in the case of repeated administration.
In 7 days after dosing 83.6% and 0.5% of dose were excreted to feces and urine respectively. Concerning the distribution of radioactivity in the gastrointestinal tract, thicker concentration was found in the contents of small and large intestine. So, the excretion of the absorbed metal to small intestine via bile tract was regarded as an important route.
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