Objective    To investigate the labeling method of peptide encoded by VEGF

189

exon 6 (QKRKRKKSRYKS) with

188

Re and evaluate the biodistribution and imaging of the

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Re labeled agents in tumor bearing nude mice.     Methods    We used S-acetyl-MAG

3

as the bifunctional chelating agent to label QKRKRKKSRYKS with rhenium-188

and the labeling conditions were optimized according to an orthogonal design. The tumor bearing mice were inj

ected via tail veins with radiolabeled peptide. The percent injected dose per gram (%ID/g) of different organs and the T/NT ratios were measured and calculated. The tumors were imaged with SPECT. All the data were analyzed with SPSS13.0.     Results    The optimized condition was tested and the corresponding labeling efficiency was 73.1±5.5%. After purification the radiochemical purity of the labeled peptide was over 95%

meanwhile the labeled agents retained a good stability and binding activity with KDR. In vivo

the uptakes of the labeled peptides in kidneys

liver

and intestine were with high radioactivity. SPECT imaging showed that labeled peptide accumulated in the tumor site. The uptake at the tumor sites was (1.846±0.511) %ID/g at 1 h while the tumor/muscle ratio was 2.43±0.30.     Conclusion   

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Re can successfully label MAG

3

-QKRKRKKSRYKS. The labeled peptides accumulate in tumors.

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Re-MAG

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-QKRKRKKSRYKS may be a promising agent for tumor imaging and therapy.