TECHNETIUM–99m LABELING OF SCORPION ANTIVENOM FOR BIODISTRIBUTION ANALYSIS

CARDOSO D. S. (1), SILVEIRA M. B. (1), RODRIGUES R. J. (2), TOLEDO V. P. C. P. (3), MORAES-SANTOS T. (4), CARDOSO V. N. (5), NUNAN E. A.

(1) Lab.de Controle de Qualidade de Produtos Farmacêuticos e Cosméticos, Faculdade de Farmácia, UFMG; (2) Divisão de Produção de Imunobiológicos, FUNED; (3) Lab. de Imunologia Clínica, Faculdade de Farmácia, UFMG; (4) Lab. de Nutrição Experimental, FAFAR/UFMG; (5), Lab. de Radioisótopos, FAFAR/UFMG.

The species Tityus serrulatus, is considered the most venomous of the South America. Serious accidents are observed in children. With the objective to carry through biodistribution analysis of the scorpion antivenom, in 21-22 day-old rats, labeling of the scorpion antivenom (fragment F(ab’)2) produced by the Fundação Ezequiel Dias (FUNED) with technetium–99m was effected. The labeling was made using two reducing agents, the stannous chloride and sodium borohydride. In order to calculate the labeling efficiency, was performed thin layer chromatography using silica gel 60 and descending chromatography with Whatman paper n° 1. Preliminary studies to stablish the optimum conditions of labeling were done. The purification was made by filtration using cellulose ester membrane. To verify stability in vitro, after the purification, 99mTc-F(ab’)2 samples were incubated with PBS pH 7,4 at 37 °C for 1, 4 and 24 h. Aliquots were then withdrawn for determination % labeling. Protection against venom lethality in mice was checked by incubation, for 30 minutes a 37 °C of 5 DL50 of Tityus serrulatus venom with various doses of labeled antivenom. The potency was determined and compared with unlabeled antivenom. In vitro the immunoreactivity of 99mTc-F(ab’)2 was verified using affinity chromatograph. An yield of labeling of 98,90±0,25% (n=3) after the purification was obtained. The labeling yield of 99mTc-F(ab’)2 after incubation remained constant. It was not observed any difference between potencies of the unlabeled (1,21 mg/mL), and labeled (1,12 mg/mL) antivenom using statistical analysis. 99mTc-F(ab’)2 presented bound with venom in vitro. This study indicate that technetium–99m labeled scorpion antivenom could be used for biodistribution analysis.

KEY WORDS: scorpion antivenom, technetium–99m, biodistribution

FINANCIAL SUPPORT: FAPEMIG

CORRESPONDENCE TO: daysamp@yahoo.com.br