The Effect of Zirconium and Sodium Citrate on the Distribution and Excretion of Simultaneously Injected Thorium and Radiostrontium by Jack Schubert

The potential health hazards of radioelements taken into the body are well known (1, 2). The present study is part of a program designed to test the effect of zirconium and other sahs on the metabolism of long lived radioelements. It has been shown that the early administration of zirconium salts to experimental animals previously injected with plutonium (Pu”~~) and radioyttrium (Ygl) resulted in a marked increase in the urinary excretion of these radioelements and a considerable reduction of their concentration in bone (3,4). Thorium (Th230) and radiostrontium (Srsg* ““) are of particular interest because of the marked differences in the nature of their deposition in bone (2). Strontium is closely related metabolically to calcium and the other alkaline earths (2) and is deposited throughout the mineral structure of bone, while many elements, including thorium, plutonium, zirconium, and the rare earths, are deposited primarily in the non-mineralized areas and possibly on the superficial surfaces of the mineralized structure (1, 2). Conditions that affect the metabolism of Ca and Sr do not appear to disturb that of Pu or Y (1, 2). It appeared unlikely, therefore, that zirconium administration would affect the metabolism of Sr. Until recently there has been little information available on the quantitative distribution and excretion of soluble thorium salts following parenteral administration (2, 6). It has been stated (2) that tracer studies and bone radioautographs showed “no significant differences between the metabolic characteristics of thorium and plutonium.” Therefore, it seemed reasonable to expect that the metabolism of injected thorium followed by zirconium administration should be markedly altered, as is the case with plutonium. It is of fundamental interest, therefore, to learn that zirconium has no significant influence on Th met,abolism. Inasmuch as the citrate salt of zirconium was used in our experiments, it was necessary to study the effects of sodium citrate as a control for the action of the citrate ion. Sodium citrate administration is of value in the treatment of experimental uranium poisoning (5) and also of lead poisoning (7), but it exerts little influence on the metabolism of plutonium and yttrium (4).