Hallaq H, Hasin Y, Fixler R, Eilam Y
Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
J Pharmacol Exp Ther. 1989 Feb;248(2):716-21.
Effects of ouabain on [Ca++]i and on contractility was measured in quin2 and fura2 loaded cultured neonatal rat cardiac myocytes. Addition of ouabain (5 x 10(-8) to 5 x 10(-6) M) to cultured myocytes exposed to balanced buffered salt solution (BSS) caused a transient increase in [Ca++]i, followed by slow oscillations for about 10 min, and by an elevated steady state level of [Ca++]i thereafter. Concentrations of ouabain between 10(-7) and 5 x 10(-7) M caused an increase in the amplitude of systolic motion (ASM) whereas concentrations above 10(-6) caused a decrease in the ASM, an increase in the beating frequency and an upward shift of the base line, indicating impaired relaxation. When ouabain was added to cardiac myocytes exposed to Ca++-free BSS the increase in [Ca++]i was not observed, but only a transient decrease. To investigate the effect of [K+]o on the ouabain-induced changes in [Ca++]i, ouabain was added to cells exposed to BSS containing low K+ concentration (1 mM instead of 5 mM in balanced BSS). In this medium the increase in ASM by ouabain was similar to that in balanced BSS. Addition of ouabain caused a transient decrease in [Ca++]i. There was no initial increase in [Ca++]i and the steady state level of [Ca++]i was not elevated as compared with the same cells before the addition of ouabain. Similar results were observed in cells loaded with quin2 or with fura2. In view of these results the mechanism of action of ouabain on cardiac myocytes is discussed.
在负载有喹啉-2（quin2）和氟罗红-2（fura2）的培养新生大鼠心肌细胞中，测量了哇巴因对细胞内钙离子浓度（[Ca++]i）和收缩性的影响。向暴露于平衡缓冲盐溶液（BSS）的培养心肌细胞中添加哇巴因（5×10⁻⁸至5×10⁻⁶M），会导致[Ca++]i短暂升高，随后约10分钟出现缓慢振荡，此后[Ca++]i的稳态水平升高。10⁻⁷至5×10⁻⁷M之间的哇巴因浓度会导致收缩期运动幅度（ASM）增加，而高于10⁻⁶的浓度会导致ASM降低、搏动频率增加以及基线向上偏移，表明舒张功能受损。当将哇巴因添加到暴露于无钙BSS的心肌细胞中时，未观察到[Ca++]i升高，仅出现短暂降低。为了研究细胞外钾离子浓度（[K+]o）对哇巴因诱导的[Ca++]i变化的影响，将哇巴因添加到暴露于低钾浓度（平衡BSS中为1 mM而非5 mM）的BSS中的细胞中。在这种培养基中，哇巴因引起的ASM增加与在平衡BSS中相似。添加哇巴因导致[Ca++]i短暂降低。与添加哇巴因之前的相同细胞相比，[Ca++]i没有初始升高，且[Ca++]i的稳态水平未升高。在负载有quin2或fura2的细胞中观察到了类似结果。鉴于这些结果，讨论了哇巴因对心肌细胞的作用机制。
