Kinetics of the Distribution and Excretion of Lead in the Rat

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Abstract
The kinetics of the distribution and excretion of lead (210Pb) were studied in rats for 14 days after single intravenous injections of 100 μg. of lead per rat. The results show that in the blood the lead is bound mainly to the cells, and that the ratio of lead in the cells and plasma is constant throughout the whole period. 210Pb is rapidly distributed in the tissues, the highest concentrations being in the kidneys, liver, and bones. The kinetics of the disappearance of 210Pb from the organs and tissues follow the pattern of first order reactions. The disappearance curves in the blood, plasma, haematic cells, and some other tissues can be expressed as sums of exponential functions. In contrast, the removal of metal from the bone tissue occurs at a constant and extremely slow rate. The metal is excreted by the faeces and urine. The rates reach their maxima within 24 hours and decrease asymptotically afterwards. More 210Pb was excreted in the faeces (35·7%) than in the urine (15·9%) during the 14 days of observation.