Tissue Distribution and Excretion of Cesium-137 in the Guinea Pig After Administration by Three Different Routes

Abstract

Data were obtained for the distribution-excretion pattern of Csl37 in guinea pigs over a period of 100 days after adminstration by 3 different routes. Three groups of 20 guinea pigs were used. Solutions of cesium chloride containing Cs137 as a tracer were administered to the animals by inhalation, by ingestion and by i.p. injection. Urine and feces were collected daily until sacrifice, and the time-tissue distribution patterns were determined after death. All measurements were made by gamma counting with a NaI(TI) detector. Since cesium chloride is extremely soluble, it was absorbed rapidly from the lungs, the digestive tract and the abdominal cavity. After the first day, the skeletal muscle had the largest concentration of Cs137. Its retention in muscle may be approximated by a single exponential function with an average biological half-life of 10 days. Concentration in other tissues did not differ significantly from that in the muscle. The Cs137 concentration in total excretion followed an exponential pattern with a rapidly and a slowly decreasing component. The average urine-to-feces ratio was 2.8. More than 95% was excreted within 32 days; at this time, approximately 65% of the remaining radioactivity was located in the skeletal muscle. A distribution and retention study of Cs137 bone tissue is in progress.