NEUROMUSCULAR ACTION OF NOVEL TOXINS FROM Crotalus durissus terrificus VENOM IN MOUSE PHRENIC NERVE-DIAPHRAGM PREPARATIONS

HERNANDEZ-OLIVEIRA, S.S.1), BORJA-OLIVEIRA, C.R.(1), TOYAMA, M.H.(1), MARANGONI, S.(1), RODRIGUES-SIMIONI, L.(2)

(1)Departamento de Farmacologia, FCM, Caixa Postal 6111, (2)Departamento de Bioquímica, IB, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brasil.

OBJECTIVES: The venom of the South American rattlesnake, Crotalus durissus terrificus, has been studied for more than a century (V. Brazil, Rev. Med. São Paulo, 6:265, 1903). In this work, we investigated the pharmacology of some novel toxins recently identified in this venom (Toyama et al., Prot. Peptide Lett., 7:381-388, 2000). METHODS AND RESULTS: Gel filtration of the venom on a column of Sephadex G-75 yielded four peaks, namely, convulxin (peak I),  gyroxin (peak II), crotoxin (peak III) and crotamine (peak IV). In contrast, molecular exclusion HPLC (Protein Pack SW 300) under isocratic conditions gave three new components, peaks IIIa, V and VI (inter-cro), in addition to peaks (I, II, III and IV) containing the principal toxins. Indirectly stimulated (0.1 Hz, 0.2 ms) mouse phrenic nerve-diaphragm preparations suspended in Tyrode solution were incubated with fractions (20 mg/ml) for up to 120 min. Crotoxin (peak III from gel filtration on Sephadex) produced its characteristic neuromuscular blockade. Peak IV from HPLC was also crotoxin and caused facilitation followed by irreversible blockade. Peak IIIa induced a slow, progressive facilitation that lasted for 120 min. Peak V showed only slight neuromuscular action. CONCLUSION: Molecular exclusion HPLC allows dissociation of the facilitatory and neuromuscular blocking actions of  crotoxin.

Financial support: CAPES, FAEP

CORRESPONDENCE TO:

HERNANDEZ-OLIVEIRA, S.S., Departamento de Farmacologia, FCM, Caixa Postal 6111, Universidade Estadual de Campinas (UNICAMP), 13083-970, Campinas, SP, Brasil, Email: castrohernandez@yahoo.com