EFFECT OF DIETARY ZINC CONTENT ON ZN-65 METABOLISM IN MICE

Zn-65 is one of the induced radioactive nuclides which are generated i n power reactors. In the present experiment, several parameters of Zn- 65 metabolism were studied in mice maintained on diets with various zi nc contents from 45 to 4,500 mg/kg to evaluate the efficacy of the dil ution method for radiation protection against internal contamination w ith Zn-65. Gastrointestinal absorption of Zn-65 was suppressed and its excretion accelerated as the dietary zinc content increased over a wi de range. Clearance of Zn-65 from tissues was generally accelerated by feeding mice a high-zinc diet, but that from the femurs was not affec ted by dietary zinc content. Zinc concentrations in tissues were regul ated homeostatically up to a dietary zinc content of 1,350 mg/kg. Alth ough a significant accumulation of zinc occurred in the liver, pancrea s, kidneys, and femurs when mice were given 4,500 mg/kg diet, the conc entrations except in the femurs recovered within a few days after swit ching to a normal-zinc diet. These results suggest that oral administr ation of zinc is effective for preventing the absorption and for enhan cing the excretion of Zn-65 to protect the body from internal radiatio n exposure with this isotope.