Radium Retention in Mice after Single Intravenous Injection

Abstract

The retention of intravenously injected radium was studied in mice by means of whole-body 7-ray spectroscopy in order to acquire some understanding of the radium retention pattern in a laboratory mammal. This study was done with the hope that such information could eventually be applied to the interpretation of data acquired in our studies with human patients who ingested or were injected with radium thirty to forty years ago. In particular, we were interested in the validity of the power function proposed by Norris et al. (1) as a description of radium retention after intravenous injection and in the possibilities of extrapolating from mouse data to the human situation. We were also interested in evaluating the pattern of retention of radon daughters with time and in ascertaining whether the situation in mice paralleled that found by Mays et al. (2) for rats, dogs, and man. Radium-226 and the radon daughters present in small animals can be determined repeatedly by external y-ray spectroscopy without injury to the animal. The retained radon, which does not emit 7-rays, is determined by quantitative measurement of its short-lived daughters, RaB(Pb214) and RaC(Bi214), by a refinement of a method proposed by Gustafson and Marinelli (3). The Ra226 content is determined by stripping the RaB and RaC spectra from the gross y-ray spectrum of the animal. This method is limited to small animals and to small biological specimens where absorption and scattering of the y-rays within the test object are minimal. This paper deals with an intensive study of four young adult female mice after each had received an intravenous injection of Ra226 bromide. Preliminary findings (4) encouraged us to pursue these studies further and to apply electronic computer techniques in the analyses of the data. The results obtained, which are presented here, formed the basis for subsequent investigations dealing with other aspects of radium metabolism in the mouse and in man, which will be described in forthcoming reports. METHODS