ynthesis of 3H-labelled bilirubin is described.3H-bilirubin is prepared by the reduction of biliverdin using sodium boro-[3H]-hydride in methanol solvent.But biliverdin is synthesized through dehydrogenation of bilirubin with 2

3-dichloro-5

6-dicyanobenzoquinone（DDQ）in dimethyl sulphoxide and sodium boro-[3H]-hydride is produced by exchange of sodium boro-hydride with tritium gas using nickel catalyst at high temperature.The specific activity of obtained 3H-bilirubin is 306GBq/mmol

while the radiochemical purity is over 95% by HPLC and paper chromatography.The permeatied profile of 3H-labelled bilirubin in rat brain has been satisfyingly obtained in animal experiments.