In Vivo Experiment on the Metabolism of Cesium in Human Blood with Reference to Rubidium and Potassium

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Two single doses of coupled radioisotopes of ¹³²Cs-⁸⁶Rb and ¹³²Cs-⁴²K were orally administered to a human subject. Body retention, urinary and fecal excretions as well as the plasma and erythrocytes contents of radioisotopes were determined. The proportion of urinary to fecal excretion was found different in cesium and rubidium, the urinary excretion being 85.3% of the total in the former and only 68.1% in the latter. Loss of cesium in the sweat amounted to 1.5 and 3.5% of the total excretion for the first two days. Uptake by the plasma of oral dose was rapid and the whole blood content reached max. 11.4% of the dose of cesium at 1 hour, while 2.9 and 2.4% respectively of rubidium and potassium was reached. The levels in the erythrocytes seemed to grow at a slower rate in cesium than in the other alkali elements. The different feature of blood metabolism found in the alkali elements was interpreted by the slow rate of clearance of ingested cesium from blood. Daily fluctuations of fall-out ¹³⁷Cs in blood and the errors involved in the assessment of the total body burden of ¹³⁷Cs by blood analysis were also discussed.