Abstract
Large doses of 90Sr and 137Cs, singly and in combination, were injected intra-peritoneally into rats. Altered whole-body retention patterns were observed with high levels of both radionuclides; the rate of 90Sr excretion decreased, while that of 137Cs increased. Urine-to-feces ratios remained constant with time and were similar to those observed after administration of tracer quantities of either radionuclide. A long-term component of 137Cs retention resulted from a small fraction residing in the skeleton. Kinetics of retention of the mixtures were predictable from the behavior of the individual radionuclides.