Couraud F, Rochat H, Lissitzky S
Biochemistry. 1980 Feb 5;19(3):457-62. doi: 10.1021/bi00544a009.
Stimulation of 45Ca uptake by scorpion neurotoxins in cultured chick embryonic heart cells has been shown to be directly linked to their effect on sodium channels. This property was used to compare the activity of 15 neurotoxins from five different species to their lethal effect in the mouse and immunological properties. As scorpion neurotoxins, the alkaloid neurotoxin veratridine enhanced 45Ca uptake, and an apparent positive cooperativity between the two drugs was observed. 125I-Labeled toxin II from the scorpion Androctonus australis Hector was shown to bind to chick heart cells specifically, saturably, and reversibly with high affinity (KD = 1--3 nM in sodium-free medium) and low capacity (10--20 fmol/mg cell protein). As shown by 45Ca uptake and radioactive toxin binding experiments, the affinity of scorpion neurotoxin to heart cell receptors was dependent on external K+ concentration. Toxin binding was lowered by increasing Na+ concentration in the medium and was abolished by veratridine in a sodium (140 mM) containing medium. As previously reported for neuroblastoma cells, all these results are in agreement with the membrane potential dependence of scorpion neurotoxin affinity for its membrane receptor.
蝎神经毒素对培养的鸡胚心脏细胞45Ca摄取的刺激作用已被证明与其对钠通道的作用直接相关。利用这一特性比较了来自五个不同物种的15种神经毒素的活性与其对小鼠的致死作用及免疫特性。作为蝎神经毒素，生物碱神经毒素藜芦定可增强45Ca摄取，且观察到两种药物之间存在明显的正协同性。来自澳大利亚杀人蝎的125I标记毒素II被证明能以高亲和力（在无钠培养基中KD = 1 - 3 nM）和低容量（10 - 20 fmol/mg细胞蛋白）特异性、饱和性且可逆地与鸡心脏细胞结合。如45Ca摄取和放射性毒素结合实验所示，蝎神经毒素对心脏细胞受体的亲和力取决于外部K+浓度。培养基中Na+浓度增加会降低毒素结合，在含钠（140 mM）培养基中藜芦定可消除毒素结合。如先前对神经母细胞瘤细胞的报道，所有这些结果都与蝎神经毒素对其膜受体亲和力的膜电位依赖性一致。
