Wada A, Arita M, Kobayashi H, Izumi F
Department of Pharmacology, University of Occupational and Environmental Health, School of Medicine, Kitakyushu, Japan.
Neuroscience. 1987 Oct;23(1):327-31. doi: 10.1016/0306-4522(87)90293-4.
The binding characteristics of [3H]saxitoxin and its binding site were examined in bovine adrenal medullary cells. These cells showed a specific binding of [3H]saxitoxin which was saturable and reversible. Scatchard analysis showed a single class of high-affinity binding sites with an equilibrium dissociation constant of 5.8 nM and a maximum binding capacity of 427.2 fmoles/10(7) cells (124.2 fmoles/mg of cell protein). A Hill plot revealed that there were no co-operative interactions among the binding sites. Unlabeled saxitoxin inhibited the specific binding of [3H]saxitoxin as well as veratridine-induced 22Na influx with a similar potency as did tetrodotoxin. However, veratridine, aconitine and scorpion venom, at concentrations that increased 22Na influx, did not inhibit [3H]saxitoxin binding. These results indicate that saxitoxin binds to a specific site on voltage-dependent Na channels and inhibits the influx of 22Na. [3H]Saxitoxin would be useful for the detailed analysis of voltage-dependent Na channels in adrenal medullary cells.
研究了[3H]石房蛤毒素在牛肾上腺髓质细胞中的结合特性及其结合位点。这些细胞表现出[3H]石房蛤毒素的特异性结合，该结合具有饱和性和可逆性。Scatchard分析显示存在一类单一的高亲和力结合位点，其平衡解离常数为5.8 nM，最大结合容量为427.2 fmol/10(7)个细胞（124.2 fmol/mg细胞蛋白）。Hill图显示结合位点之间不存在协同相互作用。未标记的石房蛤毒素抑制[3H]石房蛤毒素的特异性结合以及藜芦定诱导的22Na内流，其效力与河豚毒素相似。然而，在增加了22Na内流的浓度下，藜芦定、乌头碱和蝎毒并不抑制[3H]石房蛤毒素的结合。这些结果表明石房蛤毒素与电压依赖性钠通道上的特定位点结合并抑制22Na的内流。[3H]石房蛤毒素将有助于对肾上腺髓质细胞中电压依赖性钠通道进行详细分析。
