Direct in vivo injection of 131I-GMS and its distribution and excretion in rabbit

AIM: To explore the distribution and metabolism of I-131-gelatin microspheres (I-131-GMSs) in rabbits after direct injection into rabbits' livers. METHODS: Twenty-eight healthy New Zealand rabbits were divided into seven groups, with four rabbits per group. Each rabbit's hepatic lobes were directly injected with 41.336 +/- 5.106 MBq I-131-GMSs. Each day after I-131-GMSs administration, 4 rabbits were randomly selected, and 250 mu L of serum was collected for gamma count. Hepatic and thyroid functions were tested on days 1, 4, 8, 16, 24, 32, 48 and 64 after I-131-GMSs administration. Single-photon emission computed tomography (SPECT) was taken for each group on days 0, 1, 4, 8, 16, 24, 32, 48, 64 after I-131-GMSs administration. A group of rabbits were sacrificed respectively on days 1, 4, 16, 24, 32, 48, 64 after I-131-GMSs administration. Their livers were taken out for histological examination. RESULTS: After I-131-GMSs administration, the nuclide was collected in the hepatic area with microspheres. The radiation could be detected on day 48 after I-131-GMSs administration, and radiography could be seen in thyroid areas in SPEC on days 4, 8, 16 and 24. One day after I-131-GMSs administration, the liver function was damaged but recovered 4 d later. Eight days after I-131-GMSs administration, the levels of free triiodothyronine and free thyroxin were reduced, which restored to normal levels on day 16. Histological examination showed that the microspheres were degraded to different degrees at 24, 32 and 48 d after I-131-GMSs administration. The surrounding parts of injection points were in fibrous sheathing. No microspheres were detected in histological examination on day 64 after I-131-GMSs administration. CONCLUSION: Direct in vivo injection of I-131-GMSs is safe in rabbits. It may be a promising method for treatment of malignant tumors. (C) 2010 Baishideng. All rights reserved.