Abstract: THE LABELLING CONDITIONS STUDIES OF TYR3OCTREOTIDE WITH 131I AND ITS BIODISTRIBUTION IN MOUSEFan Hongqiang Wang Fan Jin Xiaohai Cheng DamingBai Hongsheng Cheng Zhen Du Jin(Department of Isotope, China Institute of Atomic Energy, Beijing 102413)ABSTRACTThe labelling conditions of Tyr3octreotide with 131I by ChT are studied. The labelled yield is 82% by HPLC. After purification using the SepPak C18 reversedphase cartridge, the radiochemical purity is 99% by HPLC. The results of in vivo biodistribution in mouse show 131ITyr3octreotide is repidly cleared from the circulation mainly by the liver. The metabolism of 131ITyr3octreotide in tumorbearing mouse is slower than that in control mouse. At three hours after intravenous injection, good localization in tumors is observed.Key words 131I labelling Tyr3octreotide labelling condition in vivo biodistribution