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观察毒毛旋花子苷元(strophanthidin,Str)对分离豚鼠心室肌细胞内游离钙浓度([Ca2+]i)的影响。酶解分离豚鼠心室肌细胞,用Fluo 3-AM负载,激光共聚焦显微镜法测定单个豚鼠心室肌细胞[Ca2+]i的荧光密度。Str可浓度依赖性地升高[Ca2+]i,Str(10μmol.L-1)在[Ca2+]i升高达峰值时,可使细胞挛缩,而Str(1和10 nmol.L-1)对细胞形态无影响。TTX、尼索地平或升高细胞外钙可影响Str(1和100 nmol.L-1)对[Ca2+]i的升高作用,而对Str(10μmol.L-1)无明显影响。在外液中加入ryanodine或去除细胞外钙,则3个检测浓度的Str升高[Ca2+]i作用均被明显抑制。在无K+、无Na+液中,10μmol.L-1Str升高[Ca2+]i的作用减弱,而Str(1和100nmol.L-1)升高[Ca2+]i的作用无明显影响。加入TTX、尼索地平或增加细胞外的钙离子浓度,则3个检测浓度Str的作用均受到影响。提示低浓度Str对[Ca2+]i的升高作用与抑制Na+、K+-ATP酶活性无关,而与促进L-型钙通道和TTX敏感性钠通道的“slip-mode”钙电导有关;高浓度Str升高[Ca2+]i的作用则是抑制Na+、K+-ATP酶的结果。此外,Str对[Ca2+]i的升高作用还与直接作用于ryanodine受体促进内钙释放有关。
To observe the effect of strophanthidin (Str) on the intracellular free calcium concentration ([Ca2 +] i) in isolated guinea pig ventricular myocytes. The guinea pig ventricular myocytes were isolated by enzymatic hydrolysis and the fluorescence intensity of [Ca2 +] i in single guinea pig ventricular myocytes was measured by laser confocal microscopy with Fluo 3-AM. Str concentration increased [Ca2 +] i in a concentration-dependent manner. Str (10μmol.L-1) induced a contraction of cells at the peak of [Ca2 +] i. Str (1 and 10 nmol.L- Form no effect. TTX, nisoldipine or extracellular calcium increased Str (1 and 100 nmol.L-1) effect on [Ca2 +] i, but had no effect on Str (10μmol.L-1). When ryanodine was added to the external fluid or extracellular calcium was removed, the effect of Str increased [Ca2 +] i at three concentrations was significantly inhibited. In K + -free and Na + -free liquid, the effect of [Ca2 +] i increased and the effect of Str (1 and 100nmol.L-1) increased [Ca2 +] i was not affected by 10μmol.L-1Str. Adding TTX, nisoldipine, or increasing the extracellular calcium concentration, the effects of Str at three concentrations were affected. It is suggested that the effect of low concentration of Str on the increase of [Ca2 +] i is not related to the inhibition of Na +, K + -ATPase activity but to the “slip-mode” calcium conductance of L-type calcium channel and TTX-sensitive sodium channel; High concentrations of Str increased [Ca2 +] i role is to inhibit Na +, K + -ATP enzyme results. In addition, the effect of Str on [Ca2 +] i is also related to the direct effect of ryanodine receptors on the release of Ca2 +.