Use of the information from experiment by animal

In order to calculate the radiation dose to various parts of human body tissue from internally deposited radionuclides, we need to know their pattern of uptake and retention within the human body. In the case that appropriate data for man are not available it is commonly necessary to use data collected from experimental animals. Since animal experiment can offer analytical approaches to the subject, the information from the experiment is considered to be rather essential for biologically logical description of the metabolism of the radionuclides. The animal experiment can be divided into three categories by the purpose; i.e., construction of a quantitative metabolic model, evaluation of the factors affecting the parameters used in the model and understanding the mechanisms of the metabolism. Extrapolation of animal data to man are subject to considerable criticism, and probably justifiably so because of the variations among species. An example of species variability is the difference of the whole-body retention rate of radiocesium between newborn of rat and human. Until adequate experimental data are collected from human subjects, we have no choice to rely mainly on information from experimental animals. As our knowledge is insufficient to provide a strong theoretical basis for the extraporation from animal to human, we should be very careful at the practice of the extrapolation, moreover, we should promote the study to establish a good interspecies correlation which will provide a better basis for the extrapolation. (auth.)