| Autor: |
Yuhi, Tomoaki, Wada, Akihiko, Yamamoto, Ryuichi, Urabe, Masanobu, Niina, Hiromi, Izumi, Futoshi, Yanagital, Toshihiko |
| Zdroj: |
Naunyn-Schmiedeberg's Archives of Pharmacology; 1994, Vol. 350 Issue 2, p209-212, 4p |
| Abstrakt: |
We have previously reported that in bovine adrenal chromaffin cells Ptychodiscus brevis toxin-3 (PbTx-3) does not alter the veratridine-induced Na influx when given alone, but increases the influx of Na when co-applied with either α- or β-scorpion venom (Wada et al. 1992). In the present study, we characterized [H]PbTx-3 binding in bovine adrenal chromaffin cells. [H]PbTx-3 binding was saturable, reversible and of high-affinity with an equilibrium dissociation constant (K) of 32.0±4.9 nmol/1 and a maximum binding capacity B of 6.2 ± 1.2 pmol/4 × 10 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 [H]PbTx-3 binding with an IC of 31 nmol/l. However, tetrodotoxin, veratridine, α- and β-scorpion venom, or veratridine in combination with either α- or β-scorpion venom did not alter [H]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. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
Full text from SpringerLink