Comparison of biodistribution of 3H, 32P and 99mTc labeled Gpp(NH)p in tumor bearing hamsters.

Biodistribution and tumor uptake studies were carried out with intravenously injected tracer doses of Gpp(NH)p labeled with 3H, 32P or 99mTc . Syrian golden hamsters with cheek pouch carcinomas, induced by repeated topical applications of DMBA, were used as a tumor model. The biodistributions of these three radionuclides were different, indicating significant molecular cleavage of this nucleotide analog. It was also apparent that this compound labeled with 99mTc may not be useful for tumor imaging due to low tumor-to-blood specific activity ratio. The cheek pouch carcinoma tumor model may be valuable for the evaluation of tumor localizing radiopharmaceuticals.