Poster 157 - Biodistribution of gyroxin using iodine-125 as radiotracer

Poster 157. Congresso da Sociedade Brasileira de Toxinologia, 8., Symposium of the Pan American Section of the International Society on Toxinology, 8., 2004, Angra dos Reis, Brasil. Abstracts... J. Venom. Anim. Toxins incl.Trop. Dis., 2004, 10, 3, p.516.

¹Alves da Silva, J.A.; ²Muramoto, E.; ¹Ribela, M.T.C.P.; ¹Rogero, J.R.; ¹Camillo, M.A.P.

1 Centro de Biologia Molecular, 2 Centro de Radiofarmácia. Instituto de Pesquisas Energéticas e Nucleares. Av. Prof. Lineu Prestes, 2242. Cidade Universitária/SP. 05508-900

Gyroxin is a serine protease toxin isolated from Crotalus durissus terrificus venom which is responsible for a neurotoxic syndrome called barrel rotation. The purpose of this work was to investigate the gyroxin toxinokinetics in vivo and to achiveknowledge of its action mechanism.

Gyroxin was isolated by affinity chromatograph and gel filtration of lyophilized venom obtained from CEVAP. Since iodine-125 is widely used as a radiotracer in biodistribution assays for identification of targets organs, incorporation tissue and biodisponibility parameters, small amount of the toxin was labelled with the radioaisotope. The classical method of chloramine T was used for its radioiodination. The labelled gyroxin integrity and purity were confirmed with SDS-PAGE 15%, discontinous system. The biodistribution assay was carried out in B10PL mice and all procedures followed COBEA protocols. The animals were separated into ten groups with three animals each. The dose injected was 8,3x10⁵Bq/100µL, via i.v., and they were sacrificed after different time intervals. Blood samples were collected and organs were separated, weighted and analyzed in gamma counter. The results were expressed as percentage of injected dose per gram of tissue (%D/g). The data allowed to differentiate the organs into three groups. The first group was the organs that followed the blood kinetics: lung, heart and brain. The second group, was the metabolisms organs and eliminations: liver, kdney and intestine. In the third group, the gyroxin concentration increased in the organs along the observation period: spleen, skeletal muscle and stomach. The radioactivity found in plasma and total blood was similar. The absence of radioactivity in the thyroid confirmed the purity of the tracer and suggested that the metabolism of the iodinated gyroxin was very slow.