Absorption, Distribution and Excretion of 14C-Probimane in Mice Bearing Lewis Lung Carcinoma 447 Animals and Tumor Models: C57BL/6j strain mice were purchased from Shanghai Center of Laboratory Animal Breeding, Chinese Academy of Sciences and experimentations were conducted in compliance with the Guidelines for the Care and Use of Research Animals, NIH, established by the Washington University’s Animal Studies Committee. C57BL/6j mice (mean body weight 21.6g) were implanted sc with LLC (5×106 cells) from donor mice. 14C-Pro 12mg was dissolved in 1 ml of normal saline at normal temperature. On day 17, mice were orally administered with 14C-Pro 120mg/Kg (about 0.2ml drug per mouse) and all mice were unlimitedly given food and water during the whole experiment. All mice were collected for their urine and feces in specialized-tailored glassy cages containing bottom tube for urine collection and intermediate mesh for collecting feces and these mice were sacrificed 2, 24 and 48 hrs after the injection of 14C-Pro. Then the blood (20µl), different organs of mice, primary tumors and pulmonary metastatic foci (approximately 3–10mg each – carefully weight and record organ weight) were separately collected in radioactive isotope couture. Exactly 0.1ml of formic acid and H2O2 were separately added to each testing-tube, then change in temperature up to 80°C for 45min for total digestion of tissues was observed. Then 5ml of ethylene glycol mono-ethyl/xylene mixture containing 0.5%PPO (5-phenyloxazolyl benzene) and 0.01%POPOP {1,4-bis-2-(5- phenyloxazolyl)benzene} was added and radioactivity in the counter was detected by an auto-liquid-scintillate (YSJ-78) PR China. The radioactivity of urine and feces were also detected after 24 and 48hrs in the same way. This experiment was triplicated and all the data were statistically treated. Results The absorption and distribution of 14C-probimane in mice: The distribution of 14C-Pro in mice bearing Lewis lung carcinoma (3LL) is manifested in Table1. Table1 showed that the extents of 14C-Pro in different normal organs of mice at 2 hrs were very high and dramatically declined at 24 and 48 hrs. Only about 1/10 of Pro remained after 14C-Pro was given at 48hrs comparing with those at 2hrs only except bowel and metastatic tumors. A persistent accumulation of Pro in metastatic tumors was observed. However the radioactivity in metastatic foci was slightly changed within 2 days. Almost no change in the Pro concentrations was observed in pulmonary metastatic nodules in the whole experiment and maintained in a high data within 48hrs. However, the radioactivity in primary tumors, though better than other normal tissues declined faster than metastatic tumors. The Pro ratios of metastatic tumor over primary tumor were 2.0, 4.4 and 15.8 at 2, 24 and 48 hrs, respectively. This evidence is a useful piece of information for the explanation of high inhibitions against neoplasm metastases by Pro and other Biz compounds. In addition, the 14C-Pro in brain was relatively low. It suggests that 14C-Pro might hardly penetrate into the blood-brain-barrier to eliminate and kill brain tumors or metastasized tumors unto brains. The 14C-Pro concentrations in gall bladders and intestines of mice at 2hrs are also very high. It suggests that 14C-Pro is soluble in both aquatic and organic tissues of the bodies. The 14C-Pro concentration in blood was declined very fast and only about 1% of 14C-Pro maintained in blood after 48hrs compared with those in 2hrs. Sci Pharm. 2010; 78: 445–450.