硝苯地平对心室肌细胞L型钙通道状态依赖性阻滞的研究

Study of state block by nifedipine of L-type calcium channels in ventricular myocyte

目的探讨选择性L型钙通道阻滞剂硝苯地平对L型钙流[ICa(L)]浓度、状态依赖性阻滞作用的影响。方法采用膜片钳全细胞记录技术对豚鼠单个心室肌细胞,给予35℃的各种含药物细胞外液快速灌流,记录ICa(L)。结果①保持电位-80mV,硝苯地平抑制ICa(L)的IC50为0.3μmol·L-1;保持电位为-40mV时,IC50为0.05μmol·L-1,呈浓度依赖性阻滞。硝苯地平0.3μmol·L-1作用于电压依赖的ICa(L)失活曲线,使其左移17mV,至更负的膜电位,显示硝苯地平相对选择与失活态钙通道结合。②在10s的静息间隔药物作用时间后的第1个实验刺激,硝苯地平3μmol·L-1或30μmol·L-1加速ICa(L)的失活,提示硝苯地平对ICa(L)可能存在激活态阻滞。结论在生理条件下,硝苯地平对ICa(L)的阻滞呈浓度、状态依赖性。相对选择与失活态钙通道结合,且可能存在激活态阻滞。

Objective We studied concentration-dependent,state-dependent of L-type calci-um current (I Ca(L) )blocked by nifedipine.Methods Wholecell membrane-potential,membrane-cur -rent was acquired during wholecell voltage clamp protocols in singular ventricular myocyte of guinea pig and recorded I Ca(L) .Re sults With Cs + -rich pipette so lu tion(-80mV holding potential),half-maximal inhibition dose(IC 50 )of nifedip ine for peak at+10mV was0.3μmol·L -1 .At holding po-ten tial-40mV,IC 50 decreased to0.05u mol·L -1 .nifedip ine shifted steady state inactivation curve of I Ca(L) toward negative potential by17mV in mid potential of curve,indicating preferential block of in activated L-type Ca 2+ channels.With K + -rich pipette so lu tion,nifedipine(3and30μmol·L -1 )accelerated I Ca(L) inactivation on first test pulse.Conclu sion In physiological condi tion,nifedipine suppresses I Ca(L) in a voltage,con centra tion and state-depen dent manner,which might be caused by its high affinity to inactivated state of chan nel,and maybe blocks L-type calcium channels in open state.[