14 

 STRONTIUM IN MAN AND BEAST 



J. F. LOUTIT 



Medical Research Council Radiobiological Research Unit, 

 Atomic Energy Research Establishment, Harwell, England 



Strictly speaking the subject of this communication and of that on Radio- 

 active Fission-Products in the Food Chain (p. 209) is not radiobiology. This 

 branch of science might be defined as the study of the effects of radiations on 

 living cells and organisms. Nevertheless, since in the present and future state 

 of the world ionizing radiation will be liberated in tissue by artificially 

 produced radio-active materials, a prerequisite of radiobiological investi- 

 gation is an understanding of how each particular radio-active nucleide is 

 dealt with by the organism and where it is ultimately most concentrated. 



To most of us, medically qualified and lay, the most important con- 

 sideration is for ourselves — man. However, from the investigator's point of 

 view, man presents some difficulties which can be overcoine with experi- 

 mental animals. Consequently, it is also necessary to elucidate in any series 

 of investigations how good a model the mouse, rat, rabbit, etc., is of man. 



If we turn now to radio-active strontium produced in nuclear fission, two 

 isotopes assume particular importance, firstly because of their long half-lives 

 (Tj) — ^^Sr 50 days and ^''Sr 28 years — and secondly because, being emitters 

 of jS-particles only, any radiation from them will have an intensely localized 

 eflfect. ^^Sr and isotopes of higher mass-number are also fission-products, 

 but as their half-lives are only a few hours or less they present no particular 

 biological hazard. The stable strontium in nature is a mixture of ^*Sr, 

 ^^Sr, ^^Sr and mainly ^^Sr. This still leaves a number of other possible 

 isotopes which can be produced in cyclotrons or reactors, and among them 

 ^^Sr (rj = 65 days) and a metastable state of ®"Sr (7^ = 2-8 hours) have 

 proved useful as tracers, both being emitters of y-rays only. 



Although the metabolism of strontium was studied sporadically before the 

 advent of nuclear fission, a greatly increased effort has been exerted in the last 

 fifteen years. Since the first publications after World War II by Hamilton^ 

 and his colleagues from Berkeley who administered ^^Sr to rats, it has been 

 confirmed in a variety of small laboratory animals that the behaviour of 

 strontium in vivo is in general similar to that of calcium. More recently the 

 observations have been extended to the larger animals, particularly ruminants 

 which are so important in our nutritional economy. 



Certain features are common to the various species investigated. For 

 instance, the strontium retained is stored in bone where its biological turn- 

 over is extremely slow; and the uptake by the normal route from the gut is 

 much greater in the infant and adolescent than in the adult. On the other 

 hand, the different animals vary somewhat in their methods of excretion. 

 In some animals the route is mainly from the gut, in others mainly in urine. 

 In the case of the ruminant, we are particularly concerned with the excretion 



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