Meyer R, Linz K W, Surges R, Meinardus S, Vees J, Hoffmann A, Windholz O, Grohé C
Physiological Institute, University of Bonn, Germany.
Exp Physiol. 1998 May;83(3):305-21. doi: 10.1113/expphysiol.1998.sp004115.
Gender-based differences in cardiovascular mortality may be due to a cardio-protective effect of oestrogens on the myocardium. However, mRNA expression of oestrogen receptors in myocardial tissue of the adult heart has yet to be demonstrated. Furthermore, a calcium antagonistic action of 17beta-oestradiol on myocardial tissue has been discussed. Therefore, two subjects were investigated in atrial myocytes of the human, and ventricular myocytes of guinea-pig and rat in this study. (1) Are oestrogen receptors expressed in adult myocardial cells? (2) Is there an influence of oestrogens on the L-type calcium current of cardiac myocytes? Expression of oestrogen receptors was investigated by reverse polymerase chain reaction. L-type calcium current was usually measured by the patch-clamp technique in whole-cell recording mode under selective recording conditions, i.e. overlapping currents were blocked. One series of experiments was performed in perforated patch configuration to avoid internal perfusion. 17beta-oestradiol inhibited L-type calcium current reversibly in all three species. At 10(-5) M, the inhibition was 15-20%. This inhibition was independent of the sex and the species. A full concentration response curve of 17beta-oestradiol on basal L-type current was recorded from female guinea-pig myocytes. The inhibition increased from 2% at 10(-7) M to about 30% at 10(-4) M 17beta-oestradiol. The values could be fitted by a sum of two sigmoidal functions with log EC50 values of -6.5 and -4.9 M and Hill slopes of 2.5 for both. The specificity of the 17beta-oestradiol action was tested by recording the L-type current in the presence of 17alpha-oestradiol and oestrone. 17alpha-oestradiol also inhibited the current, but with a maximal inhibition of only 17%. The concentration-response curve could be fitted by a single sigmoidal function (log EC50 -6-3 M; Hill slope 0.55). Oestrone did not influence the current at all. The decrease in L-type current after the application of 17beta-oestradiol via a rapid perfusion system developed with a time constant of 3-4 s, which was in the same range as that for the influence of isoprenaline. The isoprenaline-stimulated L-type current was much more susceptible to the inhibition by 17beta-oestradiol, i.e. in pre-stimulated cells (1) the inhibitory effect is significantly higher (e.g. at 10(-5) M, inhibition was 36.3% compared with 11.2% in untreated cells) and (2) an inhibitory effect can be seen with oestradiol concentrations as low as 10(-9) M. Although the concentrations needed to gain a calcium antagonistic influence on the basal current were much too high to explain a cardio-protective influence of oestrogens, the presence of oestrogen receptors in cardiac myocytes of all three species, together with the shift in concentration dependence following pre-stimulation by isoprenaline, suggest that myocytes are a potential target for oestrogen.
心血管疾病死亡率的性别差异可能归因于雌激素对心肌的心脏保护作用。然而，雌激素受体在成年心脏心肌组织中的mRNA表达尚未得到证实。此外，已经讨论了17β-雌二醇对心肌组织的钙拮抗作用。因此，在本研究中，对人的心房肌细胞以及豚鼠和大鼠的心室肌细胞中的两个主题进行了研究。（1）成年心肌细胞中是否表达雌激素受体？（2）雌激素对心肌细胞的L型钙电流有影响吗？通过逆转录聚合酶链反应研究雌激素受体的表达。L型钙电流通常在选择性记录条件下，即重叠电流被阻断时，采用全细胞记录模式通过膜片钳技术进行测量。进行了一系列实验采用穿孔膜片配置以避免内部灌注。17β-雌二醇在所有三个物种中均可逆地抑制L型钙电流。在10⁻⁵ M时，抑制率为15% - 20%。这种抑制与性别和物种无关。从雌性豚鼠心肌细胞记录了17β-雌二醇对基础L型电流的完整浓度反应曲线。抑制率从10⁻⁷ M时的2%增加到10⁻⁴ M 17β-雌二醇时的约30%。这些值可以用两个S形函数的和来拟合，log EC50值分别为 - 6.5和 - 4.9 M，希尔斜率均为2.5。通过在17α-雌二醇和雌酮存在下记录L型电流来测试17β-雌二醇作用的特异性。17α-雌二醇也抑制电流，但最大抑制率仅为17%。浓度反应曲线可以用单个S形函数拟合（log EC50 - 6.3 M；希尔斜率0.55）。雌酮对电流没有任何影响。通过快速灌注系统施加17β-雌二醇后L型电流的下降以3 - 4秒的时间常数发展，这与异丙肾上腺素的影响范围相同。异丙肾上腺素刺激的L型电流对17β-雌二醇的抑制更敏感，即在预刺激细胞中（1）抑制作用明显更高（例如在10⁻⁵ M时，抑制率为36.3%，而未处理细胞中为11.2%），（2）在低至10⁻⁹ M的雌二醇浓度下即可观察到抑制作用。尽管获得对基础电流的钙拮抗影响所需的浓度过高，无法解释雌激素的心脏保护作用，但所有三个物种的心肌细胞中均存在雌激素受体，以及异丙肾上腺素预刺激后浓度依赖性的变化表明，心肌细胞是雌激素的潜在靶点。
