Characterization of [3H]brevetoxin binding to voltage-dependent sodium channels in adrenal medullary cells.
Naunyn Schmiedebergs Arch Pharmacol
; 350(2): 209-12, 1994 Aug.
Article
en En
| MEDLINE
| ID: mdl-7990979
We have previously reported that in bovine adrenal chromaffin cells Ptychodiscus brevis toxin-3 (PbTx-3) does not alter the veratridine-induced 22Na influx when given alone, but increases the influx of 22Na when co-applied with either alpha- or beta-scorpion venom (Wada et al. 1992). In the present study, we characterized [3H]PbTx-3 binding in bovine adrenal chromaffin cells. [3H]PbTx-3 binding was saturable, reversible and of high-affinity with an equilibrium dissociation constant (Kd) of 32.0 +/- 4.9 nmol/l and a maximum binding capacity (Bmax) of 6.2 +/- 1.2 pmol/4 x 10(6) cells (4.5 +/- 0.9 pmol/mg cell protein). A Hill plot revealed the lack of cooperative interaction among the binding sites. Unlabelled PbTx-3 inhibited [3H]PbTx-3 binding with an IC50 of 31 nmol/l. However, tetrodotoxin, veratridine, alpha- and beta-scorpion venom, or veratridine in combination with either alpha- or beta-scorpion venom did not alter [3H]PbTx-3 binding. All these results suggest that PbTx-3 binds to a site (site 5) distinct from the previously known four toxin binding sites, which does not gate voltage-dependent Na channels by itself, but is specifically involved in the allosteric modulation of Na channels in adrenal medullary cells.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Canales de Sodio
/
Médula Suprarrenal
/
Oxocinas
/
Toxinas Marinas
/
Neurotoxinas
Límite:
Animals
Idioma:
En
Revista:
Naunyn Schmiedebergs Arch Pharmacol
Año:
1994
Tipo del documento:
Article
País de afiliación:
Japón
Pais de publicación:
Alemania