[Preparation, quality control and biodistribution of 131I-herceptin in New Zealand rabbits].
OBJECTIVE
To study the immunoactivity,biodistribution and metabolic pattern of (131)I-Herceptin in rabbits.


METHODS
Herceptin was radiolabelled with (131)I and its radiochemicalpurity (RCP) measured by size-exclusion high-pressure liquid chromatography (HPLC). The binding rate to BT-474 cells was measured to evaluate the immunoactivity of (131)I-Herceptin. (131)I-herceptin (2.0 mCi/kg) was injected intravenously into New Zealand rabbits. Scintigraphy on emission computed tomography was performed at 3 h, 1, 3 and 5 days after injection, and the radiocounts of the heart, liver and kidney etc. were compared with that of the muscle to calculate the organ-to-muscle activity ratio (O/M). On the fifth day,the rabbits were killed and the blood, myocardium, lung and other organs were obtained for measuring the radiocounts on gamma-counter to calculate the uptake percentage per gram tissue (ID%/g).


RESULTS
The labeling rate of (131)I-herceptin was 93% with RCP of 95% and binding rate to BT-474 cells of 36.9%. After injection of (131)I-herceptin, the heart, lung and liver displayed dense radioactive regions but not the muscles and intestines. Three hours after injection, the O/M ratio of the heart was significantly higher than that of the lung, kidney and intestine (P<0.05), but decreased significantly one day after injection (t=10.817, P<0.001) with further decrement on days 3 and 5 (P<0.05). The O/M ratio of liver on day 1, 3, and 5 reduced significantly in comparison with that at 3 h (P<0.05). The uptake percentage was higher in the blood (11.3 ID/g%) than in the liver (2.8 ID/g%) and the myocardium (1.8 ID/g%).


CONCLUSIONS
(131)I-herceptin possesses high immunoactivity which distributes mainly in the blood, liver and kidney, but with low uptake in the myocardium.
Department of Oncology, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China.
Yi-xiang
YX
Fan
Rong-cheng
RC
Luo
Yong-xin
YX
Fang
Xiao
X
Yan
D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000592:standards; D001667:Binding, Competitive; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics; D008297:Male; D011786:Quality Control; D011817:Rabbits; D013997:Time Factors; D014018:Tissue Distribution; D000068878:Trastuzumab
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D007457:Iodine Radioisotopes; D000068878:Trastuzumab