Effects of a toxic fraction,PhTx2, from the spider Phoneutria nikriventer on the sodium current |
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Authors: | Demetrius A. M. Arújo Marta N. Cordeiro Carlos R. Diniz Paulo S. L. Beirão |
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Affiliation: | (1) Departamento de Bioquímica e Imunologia, ICB, Universidade Federal de Minas Gerais, Cx. Postal 2486, 30161 Belo Horizonte, MG, Brazil;(2) Centro de Pesquisa e Desenvolvimento, Fundação Ezequiel Dias, Cx. Postal 026, 30550 Belo Horizonte, MG, Brazil;(3) Present address: Departamento de Fisiologia, CCBi, Universidade Federal de Alagoas, Praça Afrânio Jorge, s/n, 57010 Maceió, AL, Brazil |
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Abstract: | Summary The toxic fraction PhTx2 of the spider Phoneutria nigriventer was studied with a modified loose patch clamp technique on frog skeletal muscle. At saturating concentration (8 g/ml) potassium currents were unaffected whereas there was a 7-fold increase in the time constant of sodium current inactivation (at –13 mV test potential). The time course of tail current deactivation was at least 3-fold slower than the control. The steady state (100 ms) inactivation and the conductance activation were shifted toward more negative potentials by 12.2 and 7.0 mV, respectively. The reversal of the sodium current was shifted 7.6 mV to more negative potential. We conclude that PhTx2 prolongs the inactivation and deactivation processes of sodium ion channels. These effects may account for the toxicity of PhTx2.Recipient of a Doctoral Fellowship from the Universidade Federal de AlagoasCorrespondence to P. S. L. Beirão at the above address |
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Keywords: | Spider toxin Phoneutria Sodium current Loose patch clamp Sodium channel inactivation |
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