Distribution, Accumulation and Excretion of <SUP>210</SUP>Pb in Rats

Abstract

The distribution and elimination of 210Pb were studied after intravenous injection in male rats and the following results were obtained. 1) On the first day after the injection of 210Pb, the highest distribution of lead among organs was found in the vertebra, followed by bone marrow, femur, liver, and kidney, and organs showing low concentration were nerve, testicle, and muscle. Disappearance of 210Pb from the liver, kidney, and blood was rapid, while the radioactivity in the femur and vertebra increased up to 3 rd day after injection and then decreased slowly. 210Pb in the nerve tissue showed highest concentration on the 14 th day during the exprimental period. On the 92 nd day after injection, the highest concentration of 210Pb among the rat organs was observed in the skeleton, followed by bone marrow, spleen, cerebellum, and medulla oblongata. 2) About 58% of the dose was excreted in feces and urine during 92 days after injection of 210Pb solution. Excretion ratio in the feces was about 8.5 times greater than that in the urine. Excretion of lead in bile was 20% of the dose within 6 hr and 27% in 48 hr after injection. 3) The biological half-life of 210Pb in selected organs and tissues was calculated from the retention rate during 92 days. The values odtained were 53.3 days in the liver, 20.1 days in the kidneys, 62.3 days in the vertebra, 79.5 days in the femur, 51.9 days in the bone marrow, 37.5 days in blood, 24.3 days in the cerebrum, 23.1 days in the cerebellum, and 27.1 days in the medulla oblongata. The retention rate of 210Pb in the whole body was calculated by subtracting the radioactivity of excreta from the injected dose in 5 rats during 92 days after injection, and the following equation, representing the retention rate of 210Pb in the whole body, was derived from the obtained values : R=36.37e-0.370t+12.57e-0.0246t+51.57e-0.000993t where R is the percentage of retained lead at t days after injection. The biological half-life of 210Pb in the whole body of rats was found to consist of 3 components, 0.81 day for rapid component, 12.24 days for intermediate component, and 303.1 days for delayed component, as shown in the equation.