In Vivo Solubility of Four Forms of Barium Determined by Scanning Techniques

Abstract

Four chemical forms of ¹³³Ba were injected intramuscularly into one hind leg of rats chloride as a simple solution prepared in distilled water, and sulfate, carbonate, and fused clay forms of previously aerosolized material resuspended in distilled water. At various times after injection to about one year, the rats were individually scanned for ¹³³Ba distribution by passing them in approximately 1- cm steps past the face of a Nal crystal made operational by a scaler timing circuit. The scanning results indicated that the chloride and carbonate were equally soluble and left the injection site very rapidly. The sulfate showed a half-life of loss from the injection site of 26 days; beyond ∼ 100 days all three forms (chloride, carbonate, and sulfate) behaved similarity, with ¹³³Ba localizing primarily in bone, where it resided with a biological half-life of 460 days. The fused clay remained at the injection site with a biological half-life of about 1400 days. The ¹³³Ba that left the injection site by dissolution localized to some degree in skeleton. All data were treated mathematically in a kinetic model. With this procedure, equations for the kinetics of loss or buildup of ¹³³Ba in the injection site, skeleton, and whole body were derived. From these equations, the rate of dissolution of fused clay was calculated to be 2.3 × 10^-8 gm cm^-2 day^-l, and, for BaSO₄, 6.9 × 10^-7 gm cm^-2 day^-1