α3β2与α3β4烟碱型乙酰胆碱受体α和β亚基不同配比的药理活性研究

摘要

目的:比较α和β亚基不同配比形成α3β2和α3β4烟碱型乙酰胆碱受体(nAChR)敏感性的差异.方法:体外转录获得α和β亚基的cRNA,采用显微注射将3种不同配比(α∶β分别为1∶10、1∶1和10∶1)的cRNA注入非洲爪蟾卵母细胞,利用双电极电压钳检测受体表达情况.利用激动剂乙酰胆碱(ACh)和拮抗剂α-芋螺毒素RegⅡA (α-CTx RegⅡA)检测在3种配比条件下形成受体药理活性的差异.结果:对于α3β2 nAChR亚型,在3种配比情况下,ACh的半数有效浓度(EC50)分别为91.2 μmol/L、104.4 μmol/L和130.6 μmol/L,α-CTx RegⅡA的半数抑制浓度(IC50)分别为40.2 nmol/L、36.4 nmol/L和42.3 nmol/L.对于α3β4 nAChR亚型,在3种配比情况下,ACh的EC50分别为44.0 μmol/L、110.0 μmol/L和230.0 μmol/L,α-CTx RegⅡA的IC50分别为226.8 nmol/L、71.5 nmol/L和49.4 nmol/L.结论:α3和β4亚基比例的改变会导致α3β4 nAChR结构和药理活性的改变.α3和β2亚基比例的改变对α3β2 nAChR结构和活性没有影响.%AIM:To compared the differential sensitivity of nicotinic acetycholine receptors (nAChRs) consisting of α and β subunits with different ratios.METHODS:The cRNA of α and β subunits was obtained by in vitro transcription.The α3β2 and α3β4 nAChR subtypes were expressed in Xenopus laevis oocytes by microinjection of cRNA coding α and β subunits at α∶β ratios of 1∶10, 1∶1 and 10∶1.The pharmacological activities of nAChRs to agonist acetycholine (ACh) and antagonist α-conotoxin (CTx) RegⅡA were investigated by two-electrode voltage-clamp techniques.RESULTS:For α3β2 nAChR expressed at the ratios of 1∶10, 1∶1 and 10∶1, the EC50 values of ACh were 91.2 μmol/L, 104.4 μmol/L and 130.6 μmol/L, respectively, while the IC50 values of α-CTx RegⅡA were 40.2 nmol/L, 36.4 nmol/L and 42.3 nmol/L, respectively.For α3β4 nAChR at the ratios of 1∶10, 1∶1 and 10∶1, the EC50 values of ACh were 44.0 μmol/L, 110.0 μmol/L and 230.0 μmol/L, respectively, while the IC50 values of α-CTx RegⅡA were 226.8 nmol/L, 71.5 nmol/L and 49.4 nmol/L, respectively.CONCLUSION:The results imply that the α3 and β4 subunit stoichiometry can change the structure and pharmacological activity of α3β4 nAChR, but the stoichiometry of α3 and β2 subunits has no effect on α3β2 nAChR.