Effects of voltage-gated Na+ channel toxins from Tityus serrulatus venom on rat arterial blood pressure and plasma catecholamines.
Scorpion toxins interact with ionic channels of excitable cells, leading to a massive release of neurotransmitters. Voltage-gated Na+ channel toxins are mainly responsible for the toxic effects of scorpion envenoming and can be classified into two classes: alpha- and beta-neurotoxins. TsTX-V and TsTX-I from Tityus serrulatus venom (TsV) are, respectively, examples of these toxins. In this work, we compared the effects of these toxins on mean arterial pressure (MAP) and catecholamines release in rats. Toxins were isolated by ion exchange chromatography (TsTX-I) followed by RP-HPLC (TsTX-V). All experiments were performed on conscious unrestrained rats previously catheterised. The toxins (15 and 30 microg/kg) and TsV (50 and 100 microg/kg) were injected intravenously. MAP was continuously monitored through femoral catheter. Epinephrine (E) and norepinephrine (NE) levels were determined by RP-HPLC with electrochemical detection, at 10 min before and 2.5, 30 and 90 min after treatments. Maximal pressor effects were observed at 2.5-3.5 min. TsV induced intense long lasting increase in MAP, as did TsTX-I. TsTX-V showed the lowest pressor effects. TsV showed the highest effects on catecholamines release, followed by TsTX-I and TsTX-V with maximal effect at 2.5 min, followed by a gradual reduction, however remaining higher than controls. Although both toxins act on Na+ channels, TsTX-I displayed significant and more intense effects on catecholamines release and blood pressure than TsTX-V. It seems that the toxicity of TsTX-V is not related only with its ability to release catecholamines, indicating that other neurotransmitters, may be involved in its toxicity.
Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, USP, Av. do Café, s/n, 14040-903 Ribeirão Preto, SP, Brazil.
Flávio
F
Vasconcelos
Vera Lúcia
VL
Lanchote
Lusiane M
LM
Bendhack
José Roberto
JR
Giglio
Suely Vilela
SV
Sampaio
Eliane Candiani
EC
Arantes
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002395:Catecholamines / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D015640:Ion Channel Gating / Q000187:drug effects*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012604:Scorpion Venoms / Q000302:isolation & purification / Q000494:pharmacology*; D012605:Scorpions; D026941:Sodium Channel Blockers / Q000302:isolation & purification / Q000494:pharmacology*; D015222:Sodium Channels / Q000378:metabolism*
D002395:Catecholamines; D012604:Scorpion Venoms; D026941:Sodium Channel Blockers; D015222:Sodium Channels