Radiation Protection in Pharmacology: The importance of experimental model to assess unexpected effects on the biodistribution of radiopharmaceutical and the action of an extract of Junglans regia.

SD Santos-Filho1, FS Carmo1, CL Diniz1, NS Pinto1, EF Frederico1, S Missaidilis3, M Bernardo-Filho1,2. 1Universidade do Estado do Rio de Janeiro, Biofísica e Biometria 20551030, Brazil, 2Instituto Nacional do Cancer, Cordenadoria de Pesquisa, Brazil, 3Open University, Department of Chemistry and Analytical Sciences, UK

Purpose: Experimental model to assess unexpected effects on the biodistribution of radiopharmaceutical due to drugs is desirable due to possible negative effects in the distribution of the radiation dose in the patient. The aim of the present study was to determine the effect of the oral ingestion of an extract of the medicinal plant Junglans regia (J. regia) on the biodistribution of the radiobiocomplex sodium pertechnetate (Na99mTcO4) in rats.

Method: The animals (female Wistar rats, 3 months old, 250-300 g), were treated with an aqueous extract of J. regia at different concentrations (5 and 0.31 mg/mL, N = 6 or 0.9% NaCl solution (control, N = 6) for 8 days. After this period of time, the rats were anesthetized and Na99mTcO4 (3.7 MBq, 0.3 mL) was injected through the ocular plexus and after 10 min the animals were sacrificed in CO2, the organs were isolated and the radioactivity present in all samples counted in a well-gamma counter. The percentage of intake radioactivity per gram (%ATI/g) of each organ was determinate. Statistical analysis were made by ANOVA test with significance of p<0.05.

Results: A significant (p<0.05) alteration in Na99mTcO4 uptake i) from 0.03 +/- 0.01 to 0.07 +/- 0.01 %ATI/g in the ovaries, ii) from 8.46 +/- 0.81 to 2.36 +/- 0.30 %ATI/g (p<0.05) in stomach and iii) from 0.63 +/- 0.21 to 0.19 +/- 0.06 %ATI/g (p<0.05) in small intestine after treatment with this extract.

Conclusions: It is expected that the distribution of the radiopharmaceutical Na99mTcO4 would be elevated in stomach, tyroid, kdneys and small intestine, this not occurred, showing the influence of J. regia on the biodistribution of this radiopharmaceutical. Although these results were obtained with animals, caution is advisable in the interpretation of the nuclear medicine examination when the patient is using this natural product. This finding is probably an example of drug interaction with a radiopharmaceutical, a fact that could lead to misdiagnosis of the examination in clinical practice with unexpected consequences for the patient.