Development of a radiolabeled beta-human chorionic gonadotropin.

beta-Human chorionic gonadotropin (beta-hCG) was successively labeled with [(67)Ga]-gallium chloride after conjugation with freshly prepared diethylenetriaminepentaacetic acid dianhydride (ccDTPA). After solid phase purification of the radiolabeled hormone, high performance liquid chromatography showed radiochemical purity higher than 95 % under optimized conditions (specific activity = 22-23 TBq mM(-1), labeling efficiency 80 %). Preliminary in vivo studies (ID g(-1), %) in male wild-type rats showed marked gonadal uptake of the tracer after 240 minutes in agreement with the biodistribution studies and reported beta-hCG receptors. Target to blood ratios were 5.1 and 15.2 after 3 and 24 hours, respectively, while target to muscle ratios were 35 and 40 after 3 and 24 hours, respectively.