Effect of Dietary Zinc Content on ⁶⁵Zn Metabolism in Mice

Abstract

⁶⁵Zn is one of the induced radioactive nuclides which are generated in power reactors. In the present experiment, several parameters of ⁶⁵Zn metabolism were studied in mice maintained on diets with various zinc contents from 45 to 4,500 mg/kg to evaluate the efficacy of the dilution method for radiation protection against internal contamination with ⁶⁵Zn. Gastrointestinal absorption of ⁶⁵Zn was suppressed and its excretion accelerated as the dietary zinc content increased over a wide range. Clearance of ⁶⁵Zn from tissues was generally accelerated by feeding mice a high-zinc diet, but that from the femurs was not affected by dietary zinc content. Zinc concentrations in tissues were regulated homeostatically up to a dietary zinc content of 1,350 mg/kg. Although a significant accumulation of zinc occurred in the liver, pancreas, kidneys, and femurs when mice were given 4,500 mg/kg diet, the concentrations except in the femurs recovered within a few days after switching to a normal-zinc diet. These results suggest that oral administration of zinc is effective for preventing the absorption and for enhancing the excretion of ⁶⁵Zn to protect the body from internal radiation exposure with this isotope.