| Objective:To evaluate the biodistribution of 99Tom labeled ethylenedicysteine(EC)-guanine in normal mice,tumor-bearing mice and mice model of inflammation so as to investigate the use of 99Tcm-EC-Guanine as a new tumor tracer for diagnosis of malignant tumor.Methods:1,The Biodistribution of Technetium-99m Labeled Guanine(99Tcm-EC-Guanine)in normal Mice.Paper chromatography was used to determine the rabeling efficiency of 99Tcm-EC-Guanine in vitro.Forty eight healthy Kunming mice were divided into 8 groups randomly.After injection of 3.7 MBq 99Tcm-EC-Guanine,these mice were sacrificed by cutting the carotid at different time.Selected tissues were excised and weighted,and the radioactivity was measured.The biodistribution of radiotracer in each tissue sample was calculated as a percentage of the injection dose per gram of wet tissue weight(%ID/g). Meanwhile,3 mice were imaged after the injection of 74 MBq 99Tcm-EC-Guanine at the same time and observed radio distribution of 99Tcm-EC-Guanine in mice.2,The Biodistribution of Technetium-99m Labeled Guanine(99Tcm-EC-Guanine)in tumor-bearing mice and mice model of inflammation.48 Lewis lung cancer tumor-bearing mice were divided into 8 groups randomly.After injection of 3.7 MBq 99Tcm-EC-Guanine,these mice were sacrificed by cutting the carotid artery at different time.Selected tissues were excised and weighed,and the radioactivity was counted.The biodistribution of radiotracer in each tissue sample was calculated as a percentage of ID/g.The ratios of tumor to blood,muscle,lung,and liver were calculated respectively(T/NT).3 Lewis lung cancer tumor-bearing mice were imaged after the injection of 18.5 MBq 99Tcm-EC-Guanine at the same time,ROIs were drawn on the images and T/B ratios were also calculated. H446 tumor-bearing mice,LOVO tumor-bearing mice and mice models of inflammation were imaged after the injection of 18.5 MBq 99Tcm-EC-Guanine and observed the radio distribution of 99Tcm-EC-Guanine in mice.Results:1,the rabeling efficiency of 99Tcm-EC-Guanine was high and stable in vitro.The blood radioactivity of 99Tcm-EC-Guanine decreased rapidlyin normal mice,99Tcm-EC-Guanine was metabolized mainly in kidney,liver uptake higher,brain did not uptake 99Tcm-EC-Guanine and the uptake of muscle was low.The%ID/g of the selected tissues was decreased rapidly in 30 minutes after injection except kidneys.2,Considerable radioactive uptake by tumor was observed,the radioactivity ratios of tumor to blood,tumor to muscle,tumor to lung and tumor to liver increased after the injection,at the 4 h the ratios of tumor to blood,muscle,lung,to liver were 1.69±0.92, 4.54±1.54,1.49±0.68,0.45±0.12 respectively.The imaging results were the same as the results of biodistribution data,and the focus was clearly visualized at the 4 h after injection. Imaging showed T/B was 4.63±0.12 at 4 h.Considerable radioactive uptake by tumor was observed in H446 tumor-bearing mice and LOVO tumor-bearing mice,the focus was clearly visualized at the 4 h after injection.The area of inflammation did not uptake 99Tcm-EC-Guanine,imaging showed T/B was 1.06±0.05 at 2 h..Conclusion:1,labeling of 99Tcm-EC-Guanine is easy,and its stability in vivo and in vitro is good. 99Tcm-EC-Guanine was metabolized mainly in kidney,the blood radioactivity of 99Tcm-EC-Guanine decreased rapidly.2,The biodistribution in Lewis lung cancer tumor-bearing mice showed that 99Tcm-EC-Guanine can be accumulated in tumor,the ratios of T/NT increase as time prolongs.The imaging of H446,LOVO tumor-bearing mice showed that 99Tcm-EC-Guanine can be accumulated in tumor,but 99Tcm-EC-Guanine did not accumulate in inflammation.99Tcm-EC-Guanine can be used as an imaging agent for purine metabolism of tumor.It can be expected that 99Tcm-EC-Guanine would be a promising imaging agent of purine for detecting malignant tumor.
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