Effects of Early Administration Times of Injected Ca-DTPA on Removal of Inhaled Plutonium Nitrate in Rats

INTRODUCTION The crucial moment of Ca-DTPA (calcium salt-diethylenetriaminepentaacetic acid) therapy for the removal of inhaled plutonium is the timing of the first injection. This is because DTPA acts on plutonium while it is in the blood, this action is lost after plutonium has been deposited into the organs. It is, therefore, generally accepted that chelation therapy should be started as early as possible after a radiation accident involving plutonium . However, the optimal timing for the first injection of Ca-DTPA is not always apparent. The commencement of Ca-DTPA injection immediately after an accident may be difficult, because of the times it takes between the measurement of the intake of inhaled plutonium into the body and the risk assessment; this measurement must be calculated before the commencement of chelation therapy. In addition, one of the important factors for controlling efficacy of Ca-DTPA is the chemical form of the inhaled plutonium. Although Ca-DTPA is effective as a compound with the soluble form of plutonium, e.g., nitrate, it has no effect on the insoluble form, e.g., oxide . In fact, we determined in a previous study that CaDTPA therapy was not effective at removing plutonium oxide from the lungs or body of rats). Inhalation is not only a possible route of plutonium intake that induces lung tumors but it is furthermore difficult to obtain the effective removal of inhaled plutonium by chelation therapy . The purpose of the present study is to clarify the effects of Ca-DTPA administration after an initial injection, we also considered the subsequent early period of therapeutic removal of inhaled plutonium nitrate in rats.