ABSTRACT
Radiotracers can be used in any situation where there is a need to follow the fate of, or track, a molecule in a biological system. Radiotracers have been used in enzyme assays, investigation into cell uptake, cell transporters, and a host of other applications. Turnover can be measured using radiotracers. The absorption, distribution, metabolism, and excretion studies are routine for new chemical entities, and they are very likely to utilize radiotracers. The chapter discusses the occasional study types, which consist primarily of DNA binding and metabolic turnover. Radioisotopes with relatively short half-lives have the advantage of higher specific activities at the start of the experiment, but DNA binding studies can be prolonged and isotopes with short half-lives may have undergone significant decay by the end of the experiment. Radioisotopes have a diversity of applications and their use is limited only by the imagination. The amount of body water in animals can be measured by isotopic dilution methods.
