Intestinal absorption and body retention of 226-radium and 47-calcium in mice: Effect of sodium alginate, measured in vivo with a Ge(Li) detector

A short review is presented of the published positive and negative results obtained with sodium alginate to reduce selectively the intestinal absorption of Sr, and of the chemical properties of alginate supposed to underlie this inhibition. Data are presented on the high efficiency of sodium alginate to diminish the absorption of²²⁶Ra: When a meal of alginated bread was given 2 hr before the administration by gastric tube of a²²⁶RaCl2 solution, the Ra-uptake in mice was reduced more than a hundredfold. In the same experiment⁴⁷Ca-uptake was reduced to only 1.2 times less than in the control animals. The effects on²²⁶Ra-absorption of different alginates, of intestinal filling with standard diet or with agar gel and of fasting are compared. The use of a coaxial Ge(Li) detector coupled with a translating and rotating sample handler allowed the direct in vivo measurement of the body-burden of²²⁶Ra and⁴⁷Ca in the same animal. The shape of the retention curve of^226Rawith, and without preventive alginate treatment could thus be compared. Starting 2 hr (= J of the transit time through the G.I. tract) after an intubation of²²⁶Ra, a therapeutic and chronic alginate treatment both reduced directly the body burden and enhanced slightly the rate of loss of²²⁶Ra. The body retention curves of²²⁶Ra are interpreted as a sequence of three different exponential loss rates.