胍丁胺对大鼠心室肌细胞L—钙通道电流的影响

目的:观察胍丁胺(Agm)对大鼠心室肌细胞L-型钙通道电流(I_(Ca-L))的影响.方法:以酶解法制备单个心室肌细胞.应用全细胞膜片箝技术记录大鼠单个心室肌细胞钙通道电流.结果:(1)Agm(0.5,1,2mmol/L)可浓度依赖性地降低电压依赖性激活I_(Ca-L)(pA)峰值,其值从1451±236 (对照组)到937±105(n=8,P<0.05),585±74(n=8,P<0.01),和301±156(n=8,P<0.01).(2)Agm 1 mmol/L使用依赖性地阻滞I_(Ca-L)·1 Hz时抑制率为53％±12％(P<0.05),3Hz时为69％±11％(P<0.01).(3)Agm使I-V曲线上移,但对I_(Ca-L)的电压依赖特征、最大激活电压以及I_(Ca-L)稳态激活无明显影响.在Agm 1 mmol/L作用下,半数激活电压(V_(0.5)和斜率参数(k)与对照组相比均无显著性差异.V_(0.5)分别为(-20.2±2.5)mV和(-20.5±2.7)mV,k分别为(3.2±0.4)mV和(3.0±0.5)mV.(4)Agm 1 mmol/L可明显使钙电流稳态失活曲线左移,加速钙通道电压依赖性稳态失活.V_(0.5)分别为(-32±6)mV和(-40±5)mV,k分别为(7.6±O.9)mV和(12.5±1.1)mV(P<0.05).(5)Agm 1mmol/L还使I_(Ca)从失活状态下恢复明显减慢.结论:Agm抑制I_(Ca-L),并主要作用于L-型钙通道的失活状态,表现为钙通道失活加速和从失活状态下恢复减慢.

Effect of agmatine on L-type calcium current in rat ventricular myocytes

AIM: To study the effect of agmatine (Agm) on L-type calcium current (I(Ca-L)) in rat ventricular myocytes. METHODS: Whole-cell configuration of the patch-clamp technique was used to record I(Ca-L) in single rat ventricular myocytes which were dissociated by enzymatic dissociation method. RESULTS: (1) Agm (0.5, 1, 2 mmol/L) reduced the voltage-dependently activated peak amplitude of I(Ca-L) (pA) from 1451+/-236 (control) to 937+/-105 (n=8, P <0.05), 585+/-74 (n=8, P <0.01), and to 301+/-156 (n=8, P <0.01) in a concentration-dependent manner. (2) Agm (1 mmol/L) blocked I(Ca-L) in a use-dependent manner. The degree of use-dependent blocking effect was 53 %+/-12 % (n=8, P <0.05) at 1 Hz, and 69 %+/-11 % (n=8, P <0.01) at 3 Hz. (3) Agm upshifted the current-voltage (I-V) curve, but the characteristics of I-V relationship were not significantly altered by Agm, the maximal activation voltage of I(Ca-L) was not different from that of control. Steady-state activation of I(Ca-L) was not affected markedly. The half activation potential (V(0.5)) and the slope factor (k) were not significantly different from those of the control. V(0.5) value was (-20.2+/-2.5) mV in the control and (-20.5+/-2.7) mV in the presence of Agm 1 mmol/L. The k value was (7.1+/-0.4) mV and (7.5+/-0.5) mV, respectively (n=8, P >0.05). (4) Agm 1 mmol/L markedly shifted the steady-state inactivation curve of I(Ca-L) to the left, and accelerated the voltage-dependent steady-state inactivation of calcium current. V(0.5) value was (-32+/-6) mV in the control and (-40+/-5) mV in the presence of Agm. The k value was (7.6+/-0.9) mV and (12.5+/-1.1) mV, respectively (n=8, P <0.05). (5) Agm 1 mmol/L markedly delayed half-recovery time of Ca2+ channel from inactivation (92+/-28) ms to (249+/-26) ms (n=8, P <0.01). CONCLUSION: Agm inhibited I(Ca-L) and mainly acted on the inactivated state of L-type calcium channel, manifested as acceleration of calcium channel inactivation and slowdown of recovery from inactivated state in rat ventricular myocytes.