Singh N P, Zimmerman C J, Taylor G N, Wrenn M E
Radiobiology Division, School of Medicine, University of Utah, Salt Lake City 84112.
Health Phys. 1988 Mar;54(3):293-9. doi: 10.1097/00004032-198803000-00006.
The concentrations and the organ distribution patterns of 228Th, 230Th and 232Th in two 9-y-old dogs of our beagle colony were determined. The dogs were exposed only to background environmental levels of Th isotopes through ingestion (food and water) and inhalation as are humans. The organ distribution patterns of the isotopes in the beagles were compared to the organ distribution patterns in humans to determine if it is appropriate to extrapolate the beagle organ burden data to humans. Among soft tissues, only the lungs, lymph nodes, kidney and liver, and skeleton contained measurable amounts of Th isotopes. The organ distribution pattern of Th isotopes in humans and dog are similar, the majority of Th being in the skeleton of both species. The average skeletal concentrations of 228Th in dogs were 30 to 40 times higher than the average skeletal concentrations of the parent 232Th, whereas the concentration of 228Th in human skeleton was only four to five times higher than 232Th. This suggests that dogs have a higher intake of 228Ra through food than humans. There is a similar trend in the accumulations of 232Th, 230Th and 228Th in the lungs of dog and humans. The percentages of 232Th, 230Th and 228Th in human lungs are 26, 9.7 and 4.8, respectively, compared to 4.2, 2.6 and 0.48, respectively, in dog lungs. The larger percentages of Th isotopes in human lungs may be due simply to the longer life span of humans. If the burdens of Th isotopes in human lungs are normalized to an exposure time of 9.2 y (mean age of dogs at the time of sacrifice), the percent burden of 232Th, 230Th and 228Th in human lungs are estimated to be 3.6, 1.3 and 0.66, respectively. These results suggest that the beagle may be an appropriate experimental animal for extrapolating the organ distribution pattern of Th in humans.
测定了我们比格犬群体中两只9岁比格犬体内228Th、230Th和232Th的浓度及其器官分布模式。这些狗像人类一样，仅通过摄入（食物和水）以及吸入接触环境本底水平的钍同位素。将比格犬体内同位素的器官分布模式与人类的器官分布模式进行比较，以确定将比格犬的器官负荷数据外推至人类是否合适。在软组织中，只有肺、淋巴结、肾脏、肝脏和骨骼含有可测量的钍同位素。钍同位素在人类和狗体内的器官分布模式相似，两种物种体内的钍大部分都存在于骨骼中。狗体内228Th的平均骨骼浓度比母体232Th的平均骨骼浓度高30至40倍，而人类骨骼中228Th的浓度仅比232Th高4至5倍。这表明狗通过食物摄入228Ra的量比人类高。狗和人类肺部232Th、230Th和228Th的累积情况有类似趋势。人类肺部232Th、230Th和228Th的百分比分别为26%、9.7%和4.8%，相比之下，狗肺部的百分比分别为4.2%、2.6%和0.48%。人类肺部钍同位素的百分比更高可能仅仅是因为人类寿命更长。如果将人类肺部钍同位素的负荷归一化至9.2年的暴露时间（处死时狗的平均年龄），则估计人类肺部232Th、230Th和228Th的负荷百分比分别为3.6%、1.3%和0.66%。这些结果表明，比格犬可能是外推人类钍器官分布模式的合适实验动物。
