IRRADIATION AND RKPLACIKMKN T OF BONE MARROW, USING i»«Au 



riiidings on total serum proteins and serum protein fractions are not 

 suiRciently conclusive to be reported at this stage. 



Days after dosing with Au 



Figure 3. Total leukocyte count for 5 rabbits receiving 



3-0 to 9-4 mC/kg dosage of ^**Au, including one rabbit 



receiving single bone-marrow transfusion at 6 days and 



4 untreated rabbits 



Insufficient time has elapsed to determine what effect, if any, the splenecto- 

 mizing of rabbits has had on the haematological situation. 



DISCUSSION OF RESULTS 



The results have shown that, using colloidal ^^^Au under the conditions of 

 this investigation, it is possible to selectively irradiate the bone marrow of 

 the rabbit to a degree which produces severe or even complete aplasia, and 

 that this can be readily achieved without producing any detectable radiation 

 damage to other organs. This is made possible l^y the relatively high uptake 

 of the colloid in the marrow, it being roughly half of the administered dose; 

 also by the fact that almost all the rest of the dose is taken up by the liver, 

 a relatively radio-resistant organ. This distribution is in contrast to that 

 observed for colloidal ^^^Au of other manufacture, administered intra- 

 venously in dogs and humans by other workers^- ^' **, who report uptakes by 

 liver, bone marrow and spleen of the order of 90,5 and 5 per cent respectively. 

 Whether we have here a species difference in distribution is not clear, but 

 it is interesting to note that distribution in the rabbit has been observed to 

 vary with variation in colloidal particle size for some materials other than 

 gold^, with higher uptake by the marrow for smaller particle sizes. Hence 

 the distribution observed in the present investigation may be due to the 

 particle size used. 



It has been reported- that homologous bone-marrow transplants have 

 been achieved in the rabbit, using whole-body radiation doses of from 800 to 

 1000 r. The rate of success rose to a maximum of 62 per cent with increasing 

 dose, but even for the successful cases 1000 r proved to be a LDj^y at 30 

 days. It would seem from this that if consistent success in replacement of 

 marrow were to be achieved, then it would be desirable to give doses of more 

 than 1000 r to the bone marrow. Since roentgen dosage measurements have 

 not been made on the tissues of survivors in the present investigation it 

 cannot be stated with certainty that they received bonc-marro\v doses 

 comparable with rabbits which died. However, the haematological findings 

 would suggest that they did and that doses around five and six times 



64 



