镉对豚鼠心脏乳头状肌动作电位及收缩力的影响

应用细胞内固定微电极技术,观察了不同浓度CdCl_2对豚鼠右心室乳头状肌快、慢反应AP及Fc的影响.结果表明20μmol/L CdCl_2对快反应APA及V_(max)无显著影响,但却抑制Fc;100和500μmol/L对上述各参数均呈抑制作用.各种剂量的CdCl_2对慢反应电位均可降低APA及V_(max),抑制Fc,缩短APD_(50)及APD_(90),对抗CaCl_2所致的正性频率作用.提示低剂量Cd使心肌细胞兴奋收缩脱耦联.可能有抗心肌Ca~(2+)流效应.

Effects of cadmium chloride on action potential and contractile force of the isolated guinea pig papillary muscle

The effects of cadmium chloride on action potentials of the guinea pig papillary muscle cells were studied by using the conventional microelectrode methods.The results showed that CdCl2(20μmol/L)produced a negative chronotropic effect and a decrease of APD50 and APD90 but had no effect on APA and Vmax Cadmium chloride(100μmol/L and 500μmol/L)showed inhibitory effecton many parameters of the action potentials including APA,Vmax,Fc,APD50 and APD90 The effects of cadmium chloride on slow action potential and contractile force(Fc)of the preparations in which the Na+channels were inactivated by partial depolarization by increasing the concentration of K+to 25.4 mmol/L were observed.APA,Vmax,Fc,APD50 and APD90 of slow action potential were decreased by cadmium chlo- ride.Furthermore,CdCl2 antagonized the positive chronotropic action to Ca2+(3.3 mmol/L)in the guinea pig right auricle.The results mentioned above suggest that cadmium chloride may make the papillary muscle cells excitation-contraction uncoupling and in-hibit Ca2+ conductance through Ca2+ channel.