A METHOD OF DISTRIBUTING BETA-RADIATION TO THE RETICULO-ENDOTHELIAL SYSTEM AND ADJACENT TISSUES 1

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Abstract
Chromic phosphate is precipitated from Na2HPO4 and Cr(NO3)3 solns. buffered by NaAc. The washed, dried percipitate is heated to 600[degree]C. The heat drives off water of crystallization and converts the soluble precipitated CrPO4 into an inert amorphous powder. This powder is ground to a colloidal state in isotonic saline by a glass-bead mill. The suspension (avg. particle size, 1 [mu]) is inert and non-toxic. As much as one mg./g. body wt. is well tolerated by mice when given intravenously. .Chromic phosphate can be prepared with radio-active P. Intraven. administered this material is taken up and retained by the reticulo-endothelial system; the [beta] radiation of P32 is distributed to the endothelial system and adjacent tissues. The material accumulates in the liver, spleen, and lungs. In the dog 90% goes to the liver, 6% to the spleen, and 2% to the lungs. In the mouse the bulk goes to the liver, but the spleen and lungs acquire more than the same organs in the dog. The CrPO4 is retained in the endothelial cells of mice for at least a year without detected decrement. Radioactive doses which delete the spleen do not affect the liver. Radioactive doses of the order of 80,000 r in the liver may induce hepatoma. The absorption of [beta] radiation in tissues is discussed with special reference to tissues less than 0.6 cms. thick.