川楝素在大鼠大脑皮层匀浆中的结合位点  

THE BINDING SITES OF￣3H-TOOSENDANIN IN RAT CEREBRAL CORTEX HOMOGENATE

作　　者：沈国光[1] 卓晓亮 施五樑 

机构地区：[1]中国科学院上海生理研究所

出　　处：《生理学报》1994年第6期546-552,共7页Acta Physiologica Sinica

基　　金：国家自然科学基金

摘　　要：从驱蛔中药楝属植物根皮提取的一种三萜化合物──川楝素是一个选择性地作用于突触前的神经肌肉传递阻遏剂。根据它作用的专一性和不可逆性推测，突触前末梢应存在着川楝素的结合位点。本工作利用３Ｈ－川楝素进行的结合实验表明，大鼠大脑皮层匀浆中存在川楝素的结合位点；３Ｈ－川楝素与结合位点复合物的平衡解离常数（ＫＤ）约为２．０×１０（－７）ｍｏｌ／Ｌ；皮层匀浆离心团粒（Ｐ２＇）的重悬液含川楝素结合位点约２．７×１０（－１２）ｍｏｌ／ｍｇ蛋白质；该结合位点的Ｈｉｌｌ系数为０．９７。研究还显示，Ｐ２＇重悬液经蔗糖密度梯度超离心得到的突触体组分是川楝素结合位点的富集亚细胞组分，其比结合活性是Ｐ２＇重悬液的２至３倍。Since early time the bark and fruit of some species of plants belonging to family melia have been used as ascaris vermifuge in traditional Chinese medicine.In our previous studies it was shown that toosendanin,a triterpenoid derivative extracted from the bark of Mell toosendan Seib et Zucc was a neuromuscular blocker acting selectively and irreversibly on the release of acetylcholine from the nerve terminals.It was thus suggested that toosendanin binding sites should exist in presynaptic nerve terminals.The binding experiments of 3H-toosendanin to the pellet of rat cerebral cortex homogenate demonstrated that the binding site of 3H-toosendanin exists in the cortex homogenate.The equilibrium dissociation constant(K.)of toosendanin-binding site complex is about 2.0×10(-7) mol/L.The specific binding activity of the homogenate pellet estimated according to the binding data is about 2.7×10(-12)mol per mg protein.The Hill coefficient of this binding site is 0.97.Our data also indicated that the synaptosomes prepared by sucrose density gradient ultracentrifugation are enriched with components of toosendanin binding site.

关 键 词：川楝素 突触前阻遏剂 结合位点 突触体 大脑皮层 

分 类 号：R285.5[医药卫生—中药学] R338[医药卫生—中医学]