TOXIC EFFECTS OF A RECOMBINANT BOTHROPSTOXIN-I ON MICE NEUROMUSCULAR JUNCTION

Oliveira, M.(1), Dal Pai-Silva M.(2), Spencer, P.J.(30, Gallacci, M. (1)

Departamentos de (1)Farmacologia e (2)Morfologia, IB, UNESP, Botucatu, SP, (3)Laboratório de Radiobiologia IPEN, SP.

Introduction: The aim of this work was to characterize the toxic effects of a recombinant bothropstoxin-I (rBthTX-I), expressed in E. coli, on mice neuromuscular junction. The neuromuscular and the myotoxic effects of rBthTX-I were comparatively evaluated to the native BthTX-I, isolated from Bothrops jararacussu venom (n-BthTX-I).  It was also evaluated the ability of heparin to neutralize both the neuromuscular and the myotoxic effects of that toxins.

Methods: Twitches were directly and indirectly evoked on sciatic nerve-extensor digitorum longus (EDL) muscle preparation by supramaximal strength pulses and recorded by a polygraph. Myotoxicity was evaluated on phrenic-diaphragm preparation by optical and electronic microscopic analysis. Both toxins were tested at 1 mM.

Results: nBthTX-I and rBthTX-I abolished indirect in 60 and 15 minutes, respectively. Direct contractions were reduced  in 70% and 90% by nBthTX-I and rBthTX-I, respectively, within 120 minutes. Both nBthTX-I and rBthTX-I induced significant muscle damage (edema, round fibers, and areas of fibers devoid of myofibrils). Pre-incubation of toxins with heparin (27.5mg/ml) prevented the blockade of both direct and indirect contractions, as well as, the muscle damage.

Discussion: This study suggests that the pharmacological profile of rBthTX-I is similar to that of nBthTX-I. In view of this, rBthTX-I could be an useful tool for future site-directed mutagenesis studies intending to clarify the structure-function relationship of BthTX-I.

Supported by:CAPES. 

CORRESPONDENCE TO:

Márcia Gallacci, Instituto de Biociências, Rubião Júnior s/n, UNESP, Botucatu, SP, CEP: 18618-000, Brasil, Email: gallacci@ibb.unesp.br