Development of a radiolabeled glucagon compound for imaging

In order to develop a possible Ga-labeled glucagon (GCG) compound for imaging studies, biosynthetic glucagon (GCG) was labeled with [67Ga]-gallium chloride after conjugation with freshly prepared diethylenetriaminepentaacetic acid dianhydride (ccDTPA). After solid phase purification of the radiolabeled hormone, high performance liquid chromatography (HPLC) and instant thin-layer chromatography (ITLC) showed a radiochemical purity around 95% in optimized conditions (specific activity = 296-370 GBq/mM; labeling efficiency 85%). Preliminary in vivo studies (ID·g-1%) in male wild-type rats showed heart:muscle, liver:muscle, lung:muscle and stomach:muscle ratios to be 5.53, 2.9, 7.56, 3.69, 3.2 (in 5 min), respectively while after 2 h liver:blood, lung:blood and spleen:blood ratios were 14.21, 16.86 and 7.8, respectively. The data suggests 5 min post injection, the tracer is accumulated in GCGR rich tissues which is in agreement with biodistribution studies and reported GCG receptors (GCGRs). The results of the present study can possibly offer a candidate for non-invasive imaging of glucagon receptor related diseased and malignancies such as glucagonoma. (authors)