Mironneau J, Martin C, Arnaudeau S, Jmari K, Rakotoarisoa L, Sayet I, Mironneau C
Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, INSERM JF 88-13, Bordeaux, France.
Eur J Pharmacol. 1990 Aug 10;184(2-3):315-9. doi: 10.1016/0014-2999(90)90624-f.
Saturable, high-affinity binding sites for [3H]saxitoxin were identified in equine portal vein smooth muscle membranes. These sites had a dissociation constant of 0.29 nM and a maximal binding capacity of 115 fmol.mg-1 of protein. A similar dissociation constant was obtained with cells prepared from rat portal vein. Specific binding of [3H]saxitoxin was completely displaced by unlabelled saxitoxin and tetrodotoxin, with inhibition constants of 0.42 and 2.10 nM, respectively. Tetrodotoxin blocked the fast Na+ current in single cells of rat portal vein in a concentration-dependent manner, with an IC50 of 3.15 nM. These results suggest that the high-affinity binding sites for tetrodotoxin and saxitoxin may be associated with voltage-dependent Na+ channels in vascular myocytes.
在马门静脉平滑肌膜中鉴定出了[3H]石房蛤毒素的可饱和、高亲和力结合位点。这些位点的解离常数为0.29 nM，最大结合容量为115 fmol·mg-1蛋白质。用大鼠门静脉制备的细胞也获得了类似的解离常数。未标记的石房蛤毒素和河豚毒素可完全取代[3H]石房蛤毒素的特异性结合，其抑制常数分别为0.42和2.10 nM。河豚毒素以浓度依赖性方式阻断大鼠门静脉单个细胞中的快速Na+电流，IC50为3.15 nM。这些结果表明，河豚毒素和石房蛤毒素的高亲和力结合位点可能与血管肌细胞中的电压依赖性Na+通道有关。
