摘要：Chemical form of cadmium in rice protein was examined in order to evaluate the toxicological effect of cadmium in rice. 1) Glutelin, one of rice proteins, was purified from commercial rice (Cd 0.10 ppm) and cadmium-polluted rice (2.2-2.5 ppm), resulting in 8 times increase in cadmium content to 0.8-1.2 ppm and 13-20 ppm, respectively. Content of zinc (117 ppm), lead (3.4 ppm), and copper (60 ppm) in the glutelin preparations from cadmium-polluted rice increased, but that of manganese (3.0 ppm) and organic phosphorus (235 ppm) decreased. 2) Glutelin-115mCd complex was prepared from purified glutelin and inorganic 115mCd salt. The cadmium content of the synthetic complex was found to be almost constant in several preparations and remarkably high (2000 ppm). The complex was stable in an alkaline medium but unstable in an acidic medium, dissociating 50% of cadmium at pH 4.0. The complex was stable against heating at 80° for 1 hr. When the complex was dialyzed against various solutions of alkali metal salts, amino acids, and metalchelaters, the complex dissociated 50% in the presence of 3×10-4M EDTA, but stable against alkali metal salts, amino acids, and some other chelaters in a final concentration of 1×10-2M. The complex dissociated completely by the addition of Hg2+ and Cu2+, and partly by the addition of Cd2+, Mg2+, Pb2+, and Zn2+ in the descending order, and was stable against Ca2+, Ba2+, and Mn2+ in a final concentration of 1×10-2M.
