99mTc-labeled field bean protease inhibitor can function as an efficient tumor detecting agent.

Purified li eld bcan prot ease inhibitor (FBPI) was labeled with 99mTc04' to asce rtain it s ability to locate tumors in tumor-bearing rat models. The labeling was done with Sn 2 + as a reducing agent and the yield was 95 %. It was stable for 2 hr at ambient temperature. The bi odistribution study of the intrav enously inj e:: ted radi olabeled FBPI in normal Wi star rat s at vario ll s time intervals showed ~ rapid blood clearance from th e systemic circulation (-5hr). Th e complex wa s predominantly exc reted throu gh th e renal and th e hepatobiliary system s. III vil'o di stribution and sc intiimaging of 99mTc_FBPI were carried ou t in rats bearing carc inogen-induced mammary tumor or tran splanted C6-gliomas. The resu lt s obtained we re compared with conven ti onal tumor-seek in g radi opharmaceuticals suc h as 99mTc-(V)dimercaptosuccinic acid (DMSA). 2olTh allous chl orid e (TIC!) and ~9mTc-Citrate. The tumor to muscle (TIM) ratios obtained with 99mTc_FBPI in rat C6 gli oma was ne arly 2 to 5-fold highcr than obta ined with all th e three conventional tumor-see kin g agents. The TIM ratio obtai ned with 'J'JrnTc_ FBPI in rat mammary tumor on th e ot her hand appeared to be 2-3-fold hi gher than noted with 9'J,nTc(V)_DMSA and 2ol T IC I. The ratio was however comparable wi th that obtain ed with 99mTc_Citrate. The st udy indicated that 99nlTc _FBPI has the specific potentials for imagin g gl iomas and possibly other tumors as well.