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Intracellular Calcium Homeostasis in the Heart

心脏细胞内钙稳态

基本信息

批准号：
03044114
负责人：
NOMA Akinori
金额：
$ 3.52万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03044114/
关键词：
Cadiac Muscle Ca Flux Cytosolic Ca Ca Channel Na-Ca Exchanger Caged Ca Whole Cell Clamp Turnover Rate 回転率細胞内Ca濃度細胞膜電流イオン輸送

项目摘要

The regulation of the cytosolic Ca^<2+> concentration is a essential process to maintain the cellular function in every type of cells. In the cardiac myocytes the influx of Ca^<2+> is conducted mainly through the Voltage-gated Ca^<2+> channel, and the efflux via the Na^+-Ca^<2+> exchanger. Namely, the depolarization of the action potential opens the L-type Ca^<2+> channels, which triggers the contraction of the muscle. During the diastole, the Na^+-Ca^<2+> exchange pump out the Ca^<2+> using the electrochemical driving force for Na^+. Under various types of pathological conditions, pumping out of Ca^<2+> is disturbed, so that the cell become overloaded with Ca^<2+>. To investigate the function of the Na^+-Ca^<2+> exchanger, we measured the membrane current, which is produced by the Na^+-Ca^<2+> exchanger (the Na^+-Ca^<2+> exchange current), simultaneously with the measurement of the intracellular free Ca^<2+>. The single ventricular myocytes were obtained by treating the guinea-pig hea … More rt with collagenase, and its membrane currents were measured using the whole cell patch clamp technique. The Ca^<2+>-indicator, Indo-1 was loaded within the cell through the whole cell patch clamp electrode. It was found that the depolarization of the membrane increased the amplitude of the outward Na^+-Ca^<2+> exchange current, and simultaneously the intracellular Ca^<2+> concentration increased. The integration of the Na^+-Ca^<2+> exchange current well corresponded to the increase of the intracellular Ca^<2+> concentration. In a separate series of experiments, the cytosolic Ca^<2+> concentration was raised instantaneously using the photolabile compound, Nitr-5. The flash photolysis of this caged Ca^<2+> activated the inward Na^+-Ca^<2+> exchange current in a single exponential time course. This finding is consistent with an Na^+-Ca^<2+> exchange model having the electrogenic step in the Na^+ transporting step. Based on the conventional exchanger model, we conclude that the turnover rate is at least 125 s^<-1> at 26 ﾟC -80 mv, and the site density is more than 2000/ mu m^2. Less

细胞内Ca^2+浓度的调节是维持细胞功能的重要过程。在心肌细胞中，Ca^<2+>内流主要通过电压门控Ca^<2+>通道进行，外流则通过Na^+-Ca^<2+>交换器进行。也就是说，动作电位的去极化打开了L-型Ca^<2+>通道，这触发了肌肉的收缩。在交换过程中，Na^+-Ca^<2+>交换利用Na^+的电化学驱动力将Ca^<2+>泵出。在各种病理条件下，Ca^<2+>的泵出受到干扰，从而使细胞变得Ca^<2+>超载。为了研究Na^+-Ca^<2+>交换体的功能，我们在测量细胞内游离Ca^<2+>的同时，测量了由Na^+-Ca ^<2 +>交换体产生的膜电流（Na^+-Ca^<2 +>交换电流）。用豚鼠心室肌细胞， ...更多信息用全细胞膜片钳技术测定其膜电流。通过全细胞膜片钳电极将Ca^<2+>-指示剂Indo-1加载到细胞内。结果表明，细胞膜去极化使细胞外Na^+-Ca^<2+>交换电流幅值增加，同时细胞内Ca^<2+>浓度也增加。Na^+-Ca^<2+>交换电流的积分与细胞内Ca^<2+>浓度的增加相对应。在另一系列实验中，使用对光不稳定的化合物Nitr-5，细胞质Ca^2+浓度瞬间升高。这种笼状Ca^2+的闪光光解激活了内向的Na^+-Ca^2+交换电流，其时间过程呈单指数变化。这一发现与Na^+-Ca^<2+>交换模型相一致，该模型在Na^+转运步骤中存在生电步骤。根据传统的交换器模型，我们得出在26 ℃-80 mv条件下，交换速率至少为125 s^<-1>，立地密度大于2000个/亩m^2。少