Modulation by bioactive substances of T-type Ca^<2+> channels and their contribution to the regulation of cardiac automaticity

T型Ca^<2>通道生物活性物质的调节及其对心脏自律性调节的贡献

基本信息

批准号：
18590201
负责人：
ONO Kyoichi
金额：
$ 2.52万
依托单位：
Akita University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

This project was carried out to investigate the functional role of the T-type Ca^<2+>channel in cardiac myocytes, particularly in pacemaker cells of sinoatrial node in relation to its possible contribution to the pacemaker activity. The following results were obtained.1) T-type Ca^<2+> channel and cardiac automaticity:The action potential and membrane currents were recorded in isolated guinea-pig sinoatrial node cells and the ionic mechanisms underlying the positive chronotropic action of PGF_<2α> and TXA_2 were investigated by the patch clamp method. We demonstrated that both PGF_<2α> and TXA_2 increased the spontaneous firing frequency of isolated sinoatrial node cells, and that this increase was caused by activation of T-type Ca^<2+> channels. The results indicate the functional role of T-type Ca^<2+> channel in the positive chronotropic action of PGF_<2α> and TXA_2.2) Electrical remodeling of L-and T-type Ca^<2+> Channels during pulmonary hypertensionWistar rats were injected with … More monocrotaline, resulting in pulmonary hypertension with right atrial and ventricular hypertrophy. The L-type Ca^<2+> channel current density was significantly decreased in right atrial cells of monocrotaline-treated rats, accompanied by a significant reduction in mRNA expression of the L-type Ca^<2+> channel CaV1.2 subunit and accessory B_2 subunit, and an increase in the B_3 subunit. On the other hand, T-type Ca^<2+> current was more marked in the right atrial cells of monocrotaline-treated rats than in those of control rats. No significant differences were observed in the mRNA expression levels of CaV3.1 and CaV3.2 or the protein level of the CaV3.1 subunit. These results indicate that pulmonary hypertension causes right atrial hypertrophy, associated with alteration of the electrophysiologic molecular properties of Ca^<2+> channels in right atrial cells.3) Functional analysis of voltage-dependent Ca^<2+> channelsNoradrenaline release from sympathetic nerve terminals is dependent on Ca^<2+> entry through neuronal voltage-gated N-type Ca^<2+> channels. The accessory β_3 subunits of Ca^<2+> channels (Cavβ_3) are preferentially associated with α1B subunit to form N-type Ca^<2+> channels, and are therefore expected to play a functional role in the stimulation-evoked release of noradrenaline. We employed Cavβ_3-null, Cavβ_3-overexpresing (Cavβ_3-Tg), and wild type (WT) mice to investigate the possible roles of Cavβ_3 in the sympathetic regulation of heart rate in vivo, and clarified the functional roles of Cavβ_3 in regulating sympathetic nerve signaling.4) Functional analysis of TRP channel proteinsThe importance of Ca^<2+> entry in the cardiac hypertrophic response is well documented, but the actual Ca^<2+> entry channels remained unknown. We demonstrated TRPC1 as a functionally important regulator of cardiac hypertrophy. We also showed that TRPC1 plays an important role in the development of hypertrophy of vascular smooth muscle cells Less

该项目是为了研究心肌细胞中T型Ca^<2+>通道的功能作用，尤其是在Sinoatrial节点的Pacemaker细胞中，与其对起搏器活性的可能贡献有关。获得了以下结果。1）T型Ca^<2+>通道和心脏自动化：动作电位和膜电流记录在孤立的豚鼠辛迪尔淋巴结细胞中，以及由PGF_<2α>和TXA_2的阳性成年机制作用的离子机制通过Patch lake lake lake lake lake。我们证明了PGF_ <2α>和TXA_2都增加了孤立的窦节点细胞的赞助频率，并且这种增加是由T型Ca^<2+>通道的激活引起的。结果表明，T型Ca^<2+>通道在PGF_ <2α>和TXA_2.2的正性表现中的功能作用）在肺高血压大鼠过程中，L-and T型Ca^<2+>通道的电气化重塑，并在肺高血压大鼠的过程中与……更多的是单独的倍增和倍增。 L型Ca^<2+>通道电流密度在单激素治疗大鼠的右心房细胞中显着降低，这是通过L型Ca^<2+>通道CAV1.2 cab1.2亚基和辅助B_2亚基的mRNA表达显着降低而实现的，而B_3亚基的增加。另一方面，与对照大鼠的T型Ca^<2+>电流在单蛋白治疗的大鼠的右心房细胞中更明显。在Cav3.1和Cav3.2的mRNA表达水平或CAV3.1亚基的蛋白质水平上未观察到显着差异。这些结果表明，肺高血压会导致右心房肥大，与右心房细胞中Ca^<2+>通道的电生理分子特性的改变有关。3）电压依赖性Ca^<2+>通道的功能分析。 Ca^<2+>通道。 Ca^<2+>通道（CAVβ_3）的辅助β_3亚基优选与α1b亚基相关联，形成N型Ca^<2+>通道，因此有望在刺激引起的非肾上腺素释放中发挥功能作用。我们使用CAVβ_3-NULL，CAVβ_3过表达（CAVβ_3-TG）和野生型（WT）小鼠研究CAVβ_3在体内心率的交感神经调节中的可能作用，并阐明CAVβ_3在控制交感神经信号的功能中的功能范围<22有充分的文献记载，但是实际的CA^<2+>进入通道仍然未知。我们证明了TRPC1是心脏肥大的功能重要调节剂。我们还表明，TRPC1在血管平滑肌细胞肥大的发展中起重要作用