Membrane potential and Na(+)-K+ pump activity modulate resting and bradykinin-stimulated changes in cytosolic free calcium in cultured endothelial cells from bovine atria.
Membrane potential and Na(+)-K+ pump activity modulate resting and bradykinin-stimulated changes in cytosolic free calcium in cultured endothelial cells from bovine atria.
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DOI：
10.1016/s0021-9258(19)39845-x
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发表时间：
1990-02
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影响因子：
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通讯作者：
R. Laskey;David John Adams;A. Johns;G. Rubanyi;C. van Breemen
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文献类型：
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作者：
R. Laskey;David John Adams;A. Johns;G. Rubanyi;C. van Breemen
用荧光分光光度法测定了Fura-2负载培养的牛心房内皮细胞膜电位对静息和缓激肽刺激的[Ca ~（2+）]i变化的影响。基础和缓激肽刺激释放的内皮源性舒张因子，监测生物测定方法，依赖于细胞外Ca 2+。同样，平台相的双相[Ca 2 +]i反应缓激肽刺激表现出依赖于细胞外Ca 2+，而初始的瞬态[Ca 2 +]i峰是难治性的细胞外Ca 2+的去除。通过改变[K+]o来确定膜去极化对缓激肽诱导的[Ca 2 +]i变化的平台期的影响。在电流钳条件下测量的静息膜电位与细胞外[K+]呈正相关（52 mV变化/[K+]o的10倍变化）。在去极化时观察到的静息和缓激肽刺激的[Ca 2 +]i变化的减少与离子转运机制一致，其中流入量与Ca 2+进入的电化学梯度（Em-ECa）线性相关。缓激肽刺激的Ca ~（2+）内流的抑制不是由于细胞外Na ~+的缺乏，因为Li ~+取代并不抑制激动剂诱导的Ca ~（2+）内流。在无K（+）的溶液中，在哇巴因的存在下，缓激肽诱发融合内皮细胞单层[Ca 2 +]i的同步振荡。这些[Ca 2 +]i之间的平台和静息[Ca 2 +]i水平的振荡依赖于细胞外Ca 2+和K+浓度。尽管血管内皮细胞中[Ca 2 +]i振荡的潜在机制尚不清楚，但这些结果表明膜电导的作用。
The effects of membrane potential on resting and bradykinin-stimulated changes in [Ca2+]i were measured in fura-2 loaded cultured endothelial cells from bovine atria by spectrofluorimetry. The basal and bradykinin-stimulated release of endothelium-derived relaxing factor, monitored by bioassay methods, were dependent on extracellular Ca2+. Similarly, the plateau phase of the biphasic [Ca2+]i response to bradykinin stimulation exhibited a dependence on extracellular Ca2+, whereas the initial transient [Ca2+]i peak was refractory to the removal of extracellular Ca2+. The effect of membrane depolarization on the plateau phase of the bradykinin-induced change in [Ca2+]i was determined by varying [K+]o. The resting membrane potential measured under current clamp conditions was positively correlated with the extracellular [K+] (52 mV change/10-fold change in [K+]o). The observed decrease in resting and bradykinin-stimulated changes in [Ca2+]i upon depolarization is consistent with an ion transport mechanism where the influx is linearly related to the electrochemical gradient for Ca2+ entry (Em - ECa). The inhibition of bradykinin-stimulated Ca2+ entry by isotonic K+ was not due to the absence of extracellular Na+ since Li+ substitution did not inhibit the agonist-induced Ca2+ entry. In K(+)-free solutions and in the presence of ouabain, bradykinin evoked synchronized oscillations in [Ca2+]i in confluent endothelial cell monolayers. These [Ca2+]i oscillations between the plateau and resting [Ca2+]i levels were dependent on extracellular Ca2+ and K+ concentrations. Although the mechanism(s) underlying [Ca2+]i oscillations in vascular endothelial cells is unclear, these results suggest a role of the membrane conductance.