METABOLIC STUDIES WITH STRONTIUM-90 THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD and water (in the same proportions as are present in whole milk); and the usual supple- Samples with very low levels of activity, such as blood and milk from injected animals and bones and excreta from infants, were sent to Nuclear Seience and Engineering Cor- poration, Pitisburgh, Pennsylvania, for assay. Bones and excreta from injected animals and those on the feeding program were assayed according to the following procedure: After dry ashing, the samples were digested with concentrated HNO,or agua regia until solution was nearly complete and then evaporated to ‘ A © -ROSY, pragnont fanole PAT, young adult « ® oy, &~TONY, adult mate @-STUPE, «© + i \ dryness. Dilute HNO, was added so that 10 ml of the final solution represented approxi- at least 30 days to allow for attainment of radioactive equilibrium. The Ca“ and Sr® beta-particle activities were measured with a cause of the wide variations in the curve shapes filtration. Aliquots of samples containing only Sr® were placed in weighed porcelain ashing capsules, evaporated to dryness, and counted with a G-M counter. In each case the appro- has two components with half times of 0.8 priate corrections were made for self-absorp- tion, and corrected counts were compared with an aliquot of the administered dose. RESULTS Distribution and Excretion of Intravenouslyadministered Sr The decline in urinary excretion rate of intravenously administered Sr® is shown in Figure 2 for four adult rhesus monkeys. Be- ¢ The reguiar diet contalns 1,395 tg of calcium per day and the low- salolum clot, 69 mg caleluin per day. specios (15, 23, 24]. Figure 4 shows the fecal excretion rate of Sr® in the two surviving adults to 900 days postinjection. The slope of the slowest component, which appears at about 200 days, was similar for the two animals despite It is quite un- DAYS AFTER INJECTION to FECAL EXCRETION OF SR-90 BY ADULT RHESUS MONKEYS for the various bones. The mean Sr:Ca ratio for the entire skeleton of this animal was 0.52. The body burdensof Sr in the two surviving adults, estimated from bone biopsy, are shown in Table IL. Average half times for Sr® were ealeulated for the male and female, based on retention 10 days after injection (57.7 percent and 36.3 percent of the administered dose respectively), and on the estimated body burdens at approximately 600 days. For the male the average half time was 470 days, and for the female, 315 days. The successive pregnancies of the female (but without lactation) appeared to hasten the elimination of Sr™. A measurable amount of Sr®, 1,540.5 dpm,’ was found in a 63.8-mg sample of vertebral ash obtained in animal that had does not seem because a great August 1955 from Alice, an not been given Sr®. This Sr” to be due to contamination, deal of care was exercised to avoid contamination during the operative and ashing procedures. DAYS AFTER INJECTION Ficore 4.~—Feral excretion rate of Srby adulf rhesus monkeys. the fact that the female had experienced three elosely spaced pregnancies. biopsy. With the exception of scapulac, paw bones, andribs, the Sr™:Ca® ratios were quite similar z apparently more efficient than that of Ca*. Similar results have been obtained for other These differences were that caudal vericbrae were selected for bone 2 and 4.2 days. A comparison of the cumulative urinary excretion of Ca* and Sr” is shown in Figure 3 for two of the adults. In contrast to the wide variation in the individual rate curves, the cumulative curves are quite similar for these two animals. Renal excretion of Sr® was various paris of the skeletons of an adult. and an adolescent monkey. The ratios Sr®:Ca‘® for the skeletal parts are shown for the adult, As might be expected on the basis of age, differences in diet, and postinjection interval, the Sr® Jevel was generally higher in the bones of the adolescent. 3 thin-end-window G-M counter by differential og for the individual animals, a scatter diagram with an average curve (broken line) is shown. The average urinary excretion curve (broken) nated bycither routeis derived from the same more striking in flat bones than in the long bones. The Sr® content of the vertebrae secins to be reasonably representative of the skeleton as a whole. It was for this reason, as well as the simplicity of the operative procedure, Ficure 3.—Cumulative urenary ereretion of Ca® and Sr? by adult rhesus monkeys. PER CENT DOSE PER Dar All samples were stored for Figure 2.-~Urinary ercretion rate of Srby adult rehesus monkeys. ROSY, @-Ca-45, O- Sr-90 TONY, av =, Ans 2 previously [22}. ol DAYS AFTER INJECTION likely that the urinary excretion-rate curve has a different shape, inasmuch as the Sr” elimi- Table I shows the distribution of Sr in the i mately 0.5 g of ash. Small aliquots were taken from samples containing both Caand Sr™, transferred to weighed gold plates, and treated according to a procedure described 177 source, namely, the circulating blood. Experiments are under way to test this point. g 1 ‘ PER CENT DOSE PER DAY Radioactive Assay Procedures CUMULATIVE EXCRETION, PER CENT ADMINSTERED DOSE e 8 s 5 3 animals were placed on a low-calcium diet ¢ consisting of fruit and vegetables; a milk substitute of butter, sugar, hydrolyzed casein ment of vitamins andiron. URINARY EXCRETION OF GA-45 AND SR-S0 or BY THE ADULT RHESUS MONKEY URINARY EXCRETION OF INTRAVENOUSLY ADMINISTERED SR-90 BY ADULT MONKEYS 2 176 | Tt Martell reports that. the error Jn measurement of Sr® by the “Chicaro Sunshine Method” used by Nuclear Science Engineering Corporation is less than £0 pereent (25), their limits of sensitivity, ‘Theactivity of this sample was well within