Development of Radiolabeled Recombinant Erythropoietin for Receptor Studies

Abstract: The study of human erythropoietin receptor is of great importance in evolution, carcinogenesisas well as endocrine research. In this study the production and quality control of human recombinanterythropoietin (EPa) has been reported. EPa was successively labeled with [670 a]-gallium chloride afterconjugation with freshly prepared cyclic DTPA-dianhydride (ccDTPA). The best results of the conjugationwere obtained by the addition of 0.5 ml of a EPa pharmaceutical solution (in phosphate buffer, pH=8) to aglass tube pre-coated with DTPA-dianhydride (0.0 I mg) at 25°C with continuous mild stirring for 30 minfollowed by HPLC/RTLC control and biological biodistribution in normal rats. Under optimizedconditions, radio-thin layer chromatography (RTLC), instant thin layer chromatography (ITLC) and highperformance 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 ratspecimen demonstrated a high liver, lung spleen, kidney as well as long bones uptake of the tracer; the factwhich is consistent with the reported EPa receptor sites. This tracer can be used in nuclear medicine andbiological studies for evaluation of EPa in vitro and/or in vivo.