Effects of a Lasiodora spider venom on Ca2+ and Na+ channels.
Toxicon
; 39(7): 991-1002, 2001 Jul.
Article
en En
| MEDLINE
| ID: mdl-11223088
The venom of a Brazilian spider, Lasiodora sp (Mygalomorphae, Theraphosidae), was screened for activity against ion channels using Ca2+ imaging and whole-cell patch clamp in GH3 cells. When tetrodotoxin (TTX) was present to block Na+ channels, the venom abolished the Ca2+ oscillations that are normally present in these cells and reduced the basal level of intracellular Ca2+. Under patch clamp, the venom reduced the L-type Ca2+ channel conductance and caused a positive shift in its voltage dependence of activation. In addition to these effects, when applied without TTX, the venom also caused a slow and noisy increase in intracellular Ca2+. The sensitivity of this second effect to TTX suggested an effect on Na+ channels, which was tested using patch clamp. Control Na+ currents inactivated completely as a single exponential. Treatment with the venom did not affect the amplitude of I(Na), but caused it to divide in two slower exponential components plus a sustained component, all of which were suppressed by TTX. The venom also caused a negative shift in the voltage dependence of activation and steady-state inactivation of I(Na). The observed effects of this venom on whole-cell currents explain the changes it causes in intracellular Ca2+ in GH3 cells and demonstrate that the venom of this spider is a source of toxins active against ion channels.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Venenos de Araña
/
Canales de Calcio
/
Canales de Sodio
Idioma:
En
Revista:
Toxicon
Año:
2001
Tipo del documento:
Article
País de afiliación:
Brasil
Pais de publicación:
Reino Unido