In this paper

bio-distribution of 99Tcm-EC-guanine in mice was evaluated using TLC and paper chromatography to determine the labeling efficiency and radiochemical purity. Forty eight healthy Kunming mice were divided in random into 8 groups

which were given with 3.7 MBq 99Tcm-EC-guanine via i.v. injection. They were sacrificed by cutting the carotid at different minutes or hours after injection for radioactivity measurement of the tissues or organs. The bio-distribution of radioactivity in the samples was calculated as a percentage of the injection dose per gram of wet tissue weight (%ID/g). Meanwhile

three normal Kunming mice and LOVO tumor-bearing mice were injected with 74 MBq 99Tcm-EC-guanine and imaged with clinical SPECT at the same time as the 8 groups after injection. The labeling efficiency of 99mTc-EC-guanine was 98% and its radiochemical purity was over 95% in 8 h. The bio-distribution in all the samples but kidney decreased rapidly in 30 minutes after injection. The results demonstrated that 99Tcm-EC-guanine was metabolized through kidney and liver

in which the %ID/g were 20.66 and 13.22 at 5 min

15.43 and 7.03 at 30 min

and 11.37 and 7.31 at 4h

respectively. The %ID/g of brain was less than 0.5 at any time. A little distribution appeared in muscle

the %ID/g were 1.11 at 30 min and 0.65 at 4 h. In heart

lung

spleen

stomach

intestine and bones

there were little distributions. The SPECT images showed similar bio-distribution. The tumor was clearly visualized in LOVO tumor-bearing mice. 99Tcm-EC-guanine

which can be labeled easily with high efficiency and radiochemical purity

is probably a good imaging agent for guanine metabolism.