doses is! chemieal distribution of the }88Ba in various bones parison * and types of bones (cortical vs. trabecular) throughout owever, ' the dog skeleton. This barium isotope was chosen because 1} it has a system’ 2 prob- ! long half-life of 7.2 years and is excellently suited for cells. | lony-term retention studies, 2) the radiation dose from it is minimal (133Ba decays by electron capture and ng 7 no beta particles are emitted), and 3) quantitative mensurements are easily made by means of seintillation counters, that is, gamma counters for whole-body retention data, and liquid seintillation counters for oentgen Am, z4 Rays on I; ‘tebrate ‘ Arbacta blood, fecal, and chemically ashed samples. MATERIALS AND METHODS ach animal was given an intravenous injection of 133Ba in the form of BaCl, in 0.073 N HCl, with a alay of i TABLE 7. ace 138, adiated ® 331-340 | of Sea . A ge at injection Dog ‘h June . A22B 576 ed Sea * Radio- A22C A22D SARI eA aS logical | hrough | ). nalian §76 te to man 1eas-agle have ntly, | with } take F l10- 1 1 0.491) 0.464) 0.427] 0.420; 0.418] 0.371] 0.332] 0.307} 293 0.252] 0.361 5 1002 1199 S13} 3113 1508 10.5 7 =7.2 kg 10.0 kg 12.5 kg B 0.667 0.647 0.589 0.588 0.610 0.509 0.460 0.401 0.224) 0.352 0.213) 0.319 0.173) 0.280 7 7 % injected dose/g calcium 1 I 0.895; 0.791 576 A22B| A22C A22D 0.667) 0.952! 0.636) 0.518} 0.460) 0.409) 0.354) 0.513 0.443 0.369 0.323 0.295 1.03 ; 0.978] 0.818 0.816/ 0.703 0.327| 0.309} 0.285] 0.280/ 0.279; 0.247) 0.221) 0.205} 0.635 0.616 0.561, 0.561 0.581 0.485 0.438 0.382 0.168) 0.344 0.149] 0.335 0.142) 0.335 0.115) 0.267 0.102) 0.277 0.1281 0.264 — 0.206 0.085) 0.251 0.196 0.105; 0.289 0.695] 0.566) 0.503; 0.447] 0.387) Percent injected dose/mg calcium Time, days 0.021 0.042 0.098 0.167 0.25 0318 1 2 3 4 5 6 7 14 1002-1091 1100-1195 1450-1850 1765-1865 Bartum: Bioop Spreciric ACTIVITY 576 — 12.83 X _ _ 1.17 « 9 — 5.15 < 2.04 X 1.18 X — _ _ 3.80 X 1.10 * —|7.40 x |4.65 x — A22B A22C _ 3.26 101/2.73 x 10-1/2.65 (2.03 _ 1.35 1016.31 x 102/1.17 — 9.5 1021.76 % 10-2/4.61 10-2!8.83 X 10-3/2.51 10-213.59 % 10-811.39 — |9.96 — (6.37 — {5.06 107°/1.66 x 1072/4.02 1077|6.28 x 10-4 18.60 x 10-6 10-6 _ 10-6 _ 13.50 x 10-8 < & & x x x X X % x x x x A22D 1072.58 1072.12 10-2}1.70 10-1/1.19 10719.57 1072|8.43 1072|3.13 1077|1.82 10-2|1.04 10-817.23 107*/4.40 10-312.39 10-211.75 x x « * x x X x x x x x X 1071 10-1 1071 1072 107 1072 107 1072 1072 10-3 1073 10-3 1073 stable barium level of 10mg/ml of solution. The in- jection materials were neutralized with NaOH immediately before injection. The age and weight of each dog at the time of injection, the quantity of %Ba injected, and the time of sacrifice are listed in Table 7 Samples of venous blood were obtained at frequent intervals on the day of injection and periodically RETENTION oF Barium TRACER 0.153] 0.201 | 0.157) 0.303 injection 300 314 0.747] 0.680 3 4 5 G 7 20 27 34 41 48 83 189 188 Mi8 454 693° 6.1 10.0 A22B} A22C|A22D| 2 | mey of ager 7.2kg 10.1 kg Fractional retention after 1 Sacrifice time, days from 9.25 yr 9.5 yr Days 0 13Ba +e injected, 6.5 yr TABLE 8. injection] Weich eight at injection, kg 8m =4 yr 156 ing its f (1966). iduced ‘ mycin IngEcTION oF Dogs witH Ba TABLE 9. 0.531 0.458 0.382 0.334 0.305 thereafter for plasma clearance studies. Separate urine and fecal samples were collected from each animal on the days indicated in Table 10. No fecal or blood sam- ples were collected from Dog 156. Preparations of samples and analyses were as follows: Whole-Body Retention The body burdens of the two long-term retention animals were measured in a steel room of the Division of Biology and Medicine by placing a 5” x 4” Nal (TI) crystal, connected to a multichannel analyzer, in a reproducible position with respect to each dog. Immediately after the intravenous injections of the iso- tope, each animal was counted so that the original count included all of the injected activity. All subsequent counts were expressed as a fraction of the origi- nal count. Also, for calibration purposes, an aliquot of the original injection solution, sealed in a glass vial, was counted in a reproducible position immediately after each dog was counted. The retention, ex- pressed as percent of injected dose per gram of total skeletal calcium, and the plasma specific activity, expressed as percent of injected dose per milligram of plasma calcium, are tabulated in Tables 8 and 9 and