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Study of the binding of 99m technetium‐radiopharmaceuticals on blood cells and plasma proteins: evaluation using precipitation with trichloroacetic acid
Author(s) -
Freitas R. S.,
Gomes M. L.,
Mattos D. M. M.,
BernardoFilho M.
Publication year - 2000
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/1099-1344(200006)43:7<663::aid-jlcr351>3.0.co;2-p
Subject(s) - chemistry , trichloroacetic acid , biodistribution , colloid , pertechnetate , radiochemistry , technetium , gold colloid , chromatography , biochemistry , colloidal gold , nuclear chemistry , in vitro , organic chemistry , nanotechnology , materials science , nanoparticle
Nuclear medicine uses radioactive tracers called radiopharmaceuticals to study the bloodflow, metabolism and morphology of an organ. Sodium pertechnetate ( 99m TcO 4 Na) and many 99m Tc products are the most frequently radiopharmaceuticals used in nuclear medicine. Secure determination of the binding of 99m Tc‐radiopharmaceuticals to plasma (P) and blood cell (BC) constituents can help to understand the biodistribution of radiopharmaceuticals. The reported evaluations about the binding of radiopharmaceuticals on blood elements have shown that the results can not be easily compared. We decided to determine the gold standard concentration of trichloroacetic acid (TCA) to study the binding of radiopharmaceuticals on blood proteins: 99m Tc‐stannous colloid ( 99m Tc‐Sn‐Colloid), sodium pertechnetate ( 99m TcO 4 Na), methylenediphosphonic acid ( 99m Tc‐MDP) and diisopropyliminodiacetic acid ( 99m Tc‐DISIDA). Blood of Wistar rats, was incubated with the radiopharmaceuticals for 5 minutes at room temperature, centrifuged and plasma (P) and blood cells (BC) were isolated. Samples of P and BC were also precipitated with TCA concentrations (0.1, 0.5, 1.0, 5.0, 10.0 and 20.0%) and soluble (SF) and insoluble fractions (IF) were isolated and counted. The percent radioactivity (%ATI) in IF‐P depends on TCA concentration. It varies from 23.7 to 75.7 ( 99m Tc‐Sn‐Colloid), from 7.8 to 26.2 ( 99m TcO 4 Na), from 10.7 to 40.4 ( 99m Tc‐MDP), from 52.2 to 60.7 ( 99m Tc‐DISIDA). The gold concentrations of TCA to study the binding of the studied radiopharmaceuticals in blood elements were revealed from the obtained results: (i) for 99m Tc‐Sn‐Colloid in the IF‐P is shown that there is no differences in the percent of radioactivity when TCA concentrations of 20 to 5.0 percent were used for precipitation, (ii) for 99m TcO 4 Na, 0.5 percent TCA concentration is the best one to precipitate the bound radiopharmaceutical, (iii) for 99m Tc‐MDP the % ATI increased from 10.7 to 40.4 with TCA concentrations from 0.1 to 5.0 percent and decreased from 40.4 to 23.8 with TCA concentrations from 5.0 to 20.0 percent and (iv) for 99m Tc‐DISIDA, the values of bound radioactivity are not dependent on TCA concentration in the range of 0.1 to 5.0 percent. The %ATI in IF‐BC depends on TCA concentration and it varied for 99m TcO 4 Na (28.8 to 77.9), for 99m Tc‐MDP (68.8 to 83.7), for 99m Tc‐DISIDA (69.3 to 92.8). However, for 99m Tc‐Sn‐Colloid, the %ATI in the insoluble fraction seems to be independent of the TCA concentration. The analysis of these results will contribute to understand the involved mechanisms on the binding of radiopharmaceuticals on blood elements. Copyright © 2000 John Wiley & Sons, Ltd.