Development of Radiolabeled Recombinant Erythropoietin for Receptor Studies

The study of human erythropoietin receptor is of great importance in evolution, carcinogenesis as well as endocrine research. In this study the production and quality control of human recombinant erythropoietin (EPO) has been reported. EPO was successively labeled with [67Ga]-gallium chloride after conjugation with freshly prepared cyclic DTPA-dianhydride (ccDTPA). The best results of the conjugation were obtained by the addition of 0.5 ml of a EPO pharmaceutical solution (in phosphate buffer, pH=8) to a glass tube pre-coated with DTPA-dianhydride (0.01 mg) at 25°C with continuous mild stirring for 30 min followed by HPLC/RTLC control and biological biodistribution in normal rats. Under optimized conditions, radio-thin layer chromatography (RTLC), instant thin layer chromatography (ITLC) and high performance liquid chromatography (HPLC) showed overall radiochemical purity of higher than 96% (specific activity=300-500 MBq/mg, labeling efficiency 77%). Preliminary in vivo studies in normal rat specimen demonstrated a high liver, lung spleen, kidney as well as long bones uptake of the tracer; the fact which is consistent with the reported EPO receptor sites. This tracer can be used in nuclear medicine and biological studies for evaluation of EPO in vitro and/or in vivo.