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Nuclear medicine uses radioactive tracers called radiopharmaceuticals to study the bloodflow, metabolism and morphology of an organ. Sodium pertechnetate (^99mTcO4Na) and many ^99mTc products are the most frequently radiopharmaceuticals used in nuclear medicine. Secure determination of the binding of ^99mTc-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: ^99mTc-stannous colloid (^99mTc-Sn-Colloid), sodium pertechnetate (^99mTcO4Na), methylenediphosphonic acid (^99mTc-MDP) and diisopropyliminodiacetic acid (^99mTc-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 (^99mTc-Sn-Colloid), from 7.8 to 26.2 (^99mTcO4Na), from 10.7 to 40.4 (^99mTc-MDP), from 52.2 to 60.7 (^99mTc-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 ^99mTc-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 ^99mTcO4Na, 0.5 percent TCA concentration is the best one to precipitate the bound radiopharmaceutical, (iii) for ^99mTc-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 ^99mTc-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 ^99mTcO4Na (28.8 to 77.9), for ^99mTc-MDP (68.8 to 83.7), for ^99mTc-DISIDA (69.3 to 92.8). However, for ^99mTc-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.

There is evidence that the biodistribution of radiopharmaceuticals may be altered by a variety of drugs. If unknown, the drug interaction with radiopharmaceuticals can lead to misdiagnosis or the necessity to repeat the examination, increasing the dose to the patient. Different substances has the ability to modify the electrophoretic mobility of the deoxyribonucleic acid (DNA). Cauliflower has the leaves used in folk medicine. We evaluated the influence of the leaf extract of cauliflower on: (i) the biodistribution of the radiopharmaceutical sodium pertechnetate (99mTcO4Na) and in (ii) the mobility of a plasmid pUC 9.1 through gel electrophoresis analysis. 99mTcO4Na (0.3ml) was administered into female Wistarrats which had drunk or not the extract for 60 days. After 10 min, the animals were sacrificed, the organs isolated, the radioactivity determined in a well counter and the percentages of radioactivity per gram (%ATI/g) in the organs calculated. The %ATI/g was not significantly altered (p>0.05) in the treated animals. The supercoiled form of the plasmid was modified by the cauliflower extract. We suggest that the action of this extract on the DNA might be explained by a direct effect or by the generation of reactive oxygen species (ROS) that could be inducing lesions in the plasmid DNA. However, this lesive effect was not capable to alter the biodistribution of the 99mTcO4Na in the treated animals with the extract.