246 GALLIUM 



Intake Levels. Gallium has been of interest biologically on account 

 of its tendency to accumulate in bone and the possibilities of diagnostic 

 and therapeutic use of Ga'- for bone malignancy in man. Since gallium 

 chloride and nitrate precipitate at the pH of blood, attention was turned 

 to the use of the citrate or lactate for injection purposes. The LD50 of 

 gallium lactate was as follows (Ga-1) : Rats, intravenous, 46 mg Ga per 

 kilogram; rats, subcutaneous, 121 mg Ga per kilogram; rabbits, intra- 

 venous, 43 mg Ga per kilogram ; rabbits, subcutaneous, 97 mg Ga per kilo- 

 gram. The intravenous toxicity of gallium citrate for the rabbit, given 

 with calcium, was 30 mg Ga per kilogram (Ga-2). There was evidence 

 that the toxicity was greater for large animals, such as dogs or goats, than 

 for rabbits (Ga-3). 



Radioassay. Routine beta or gamma counting presents no particular 

 problem. In vivo measurements are practical. Since radiation effects 

 are of primary interest, it becomes necessary to consider absolute meas- 

 urements. Methods involving standardization against radium have been 

 described (Ga-4). 



Chemistry. An analytical method has been reported for estimation of 

 2 to 100 Mg gallium in biological material (Ga-5) which is based on diges- 

 tion in H2SO4, treatment with 8-hydroxyciuinoline, and fluorescence meas- 

 urement of the chloroform extract. Procedures have been described for 

 preparation of gallium lactate and gallium citrate (Ga-6, Ga-7). 



Typical Methods. About 0.2 to 0.4 mc Ga^^ per kilogram body weight 

 (6 mg/kg) as gallium lactate was injected subcutaneously into rats and 

 rabbits (Ga-8). The animals were killed at 6 hr after dosage, and thin 

 sections of bones and teeth prepared by grinding and then mounted on 

 X-ray film for exposures of 3 to 48 hr to give autoradiograms. In another 

 study, labeled gallium citrate (0.5 mc/kg) was injected subcutaneously 

 into rabbits (Ga-9). Bone autoradiograms were made, and fresh tissues 

 were gamma-counted using an end- window tube shielded with a 1700- 

 mg/cm^ absorber. Tissues have been assayed for Ga'- by dissolving in 

 concentrated HNO:; in 10-ml volumetric flasks, making to volume, and 

 pouring into petri dishes for direct solution counting (Ga-10). Reference 



