毒毛旋花子苷元对豚鼠心室肌细胞内钙浓度的影响(英文)

Effects of strophanthidin on intracellular calcium concentration in ventricular myocytes of guinea pig

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。

Effect of strophanthidin （Str） on intracellular calcium concentration （ [ Ca2^＋ ] i ） was investigated on isolated ventricular myocytes of guinea pig. Single ventricular myocytes were obtained by enzymatic dissociation technique. Fluorescent signal of [ Ca^2＋ ]i was detected with confocal microscopy after incubation of cardiomycytes in Tyrode＇ s solution with Fluo3-AM. The result showed that Str increased [ Ca^2＋ ]i in a concentration-dependent manner. The ventricular myocytes began to round-up into a contracture state once the peak level of [ Ca^2＋ ]i was achieved in the presence of Str （ 10 μmol · L^-1 ） , but remained no change in the presence of Str （1 and 100 nmol · L^-1 ）. Tetrodotoxin （TTX）, nisodipine, and high concentration of extracellular Ca^2＋ changed the response of cardiomycytes to Str （1 and 100 nmol · L^-1）, but had no obvious effects on the action of Str（ 10 μmol · L^-1）. The elevation of [ Ca^2＋ ]i caused by Str at all of the detected concentrations was partially antagonized by rynodine （ 10 μmol · L^-1 ） or the removal of Ca^2＋ from Tyrode＇s solution. In Na^＋, K^＋-free Tyrode＇s solution, the response of cardiomycytes in [Ca^2＋ ]i elevation to Str（ 10 μmol· L^-1） was attenuated, while remained no change to Str （1 and 100 nmol· L^-1）. TTX, nisodipine, and high concentration of extracellular Ca^2＋ changed the response of cardiomycytes to Str at all of the detected concentrations in Na ^＋ , K ^＋ -free Tyrode＇ s solution. The study suggests that the elevation of [ Ca^2＋ ] i by Str at the low （nomomolar） concentrations is partially mediated by the extraeellular calcium influx through Ca^2＋ channel or a ＂slip mode conductance＂ of TTX sensitive Na^＋ channel. While the effect of Str at high （micromolar） concentrations was mainly due to the inhibition of Na^＋ , K^＋ -ATPase. Directly triggering the release of intracellular Ca^2＋ from sarcoplasmic reticulum （SR） by Str may be also involved in the mechanism of [ Ca^2 ＋] i elevation.