T-type calcium channel in sinoatrial node cells of rats after repeated exhaustive exercise

doi:10.3969/j.issn.2095-4344.2014.24.010

Abstract

Abstract:

BACKGROUND: At present, there is little evidence about the effect of exercise on T-type calcium channel (T-Ca²⁺ channel) in sinoatrial node cells.
OBJECTIVE: To analyze the subunit Cav3.1 mRNA and current density of T-Ca²⁺ channel of sinoatrial node cells after 2 weeks of repeated exhaustive treadmill exercise in rats.
METHODS: Fifty healthy male Sprague-Dawley rats were equally assigned into five groups，including one control groups (n=10; no exercise), two exhaustive exercise groups (n=20; single treadmill running at 25 m/min, 0° slope), and two repeated exhaustive exercise groups (n=20; repeated treadmill running at 25 m/min, 0° slope, once per day, 6 days per week, for 2 weeks. The samples were drawn from 10 rats in the exercise groups at 0 and 24 hours after exhaustive treadmill running respectively. The mRNA expression of T-Ca²⁺ channel subunit Cav3.1 in sinoatrial node was analyzed by real-time fluorescent quantitative PCR. The current density of T-Ca²⁺ channel was analyzed with acute isolation and whole-cell patch clamp techniques, to observe the effect of repeated treadmill exercise on T-Ca²⁺ channel.
RESULTS AND CONCLUSION: The Cav3.1 mRNA expression of the repeated exhaustive exercise groups at 0 and 24 hours were significantly lower than that of control group (P < 0.01). The current density of T-Ca²⁺ channel of the repeated exhaustive exercise groups at 0 and 24 hours were significantly lower than that of control group and single exhaustive exercise group (P < 0.01, P < 0.01). Two-week repeated exhaustive treadmill exercise can decrease the subunit Cav3.1 mRNA expression and the current density of T-Ca²⁺ channel in the sinoatrial node cells. The exhaustive exercise induced diastolic automatic depolarization and slowed down spontaneous activity of sinoatrial node cells, which may be one of the most important mechanism of exercise-induced sinoatrial node dysfunction and arrhythmia.

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

全文链接：

Key words: sinoatrial node, calcium channel, sports medicine

CLC Number:

R318

Bo Bing . T-type calcium channel in sinoatrial node cells of rats after repeated exhaustive exercise[J]. Chinese Journal of Tissue Engineering Research, 2014, 18(24): 3829-3834.

Figures/Tables 2

2.1 实验动物数量分析实验选用大鼠50只，分为5组，实验过程无脱失，全部进入结果分析。 2.2 各组大鼠窦房结T-Ca2+通道亚基mRNA表达对照组，一次力竭0 h，一次力竭24 h，反复力竭0 h，反复力竭24 h大鼠窦房结T-Ca2+通道亚基Cav3.1 mRNA相对表达量(2-△△Ct)分别为1.22±0.16，0.89±0.12，0.93±0.08，0.36±0.04，0.42±0.02。与对照组相比，一次力竭运动各组无明显差异；2周跑台训练反复力竭组0 h、反复力竭组24 h组Cav3.1 mRNA相对表达量下降，差异有显著性意义(P < 0.01，P < 0.01)，两组间差异无显著性意义。与一次力竭0 h组比较，2周跑台训练反复力竭组0 h、反复力竭 24 h组Cav3.1 mRNA相对表达量下降(P < 0.05，P < 0.05)，两组间无明显差异。表明一次力竭运动对于Cav3.1 mRNA相对表达量无明显影响；反复跑台训练可引起Cav3.1 mRNA相对表达量下降(图2)。2.3 各组大鼠窦房结T-Ca2+通道电流密度选取大鼠单个窦房结细胞为研究对象在电极外液中加入0.3 mmol/L CdCl2以阻断ICa,L，1 mmol/L BaCl2以阻断IK1通道，当形成全细胞封接后，给予细胞保持电位-40 mV，以10 mV步阶，-40 mV-+40 mV、500 ms的阶梯刺激方波，记录ICa,T电流(图3)，此电流可以被4 μmol/L Nifedipine阻断。实验结果测定-90 mV-+70 mV各条件电压下ICa,T稳态电流值与钳制电位-40 mV时的差值作为ICa,L电流值，并与其膜电容比值作为其标准化电流密度。与对照组相比，一次跑台训练组一次力竭0 h、一次力竭24 h组电流密度无明显变化，2周跑台训练反复力竭0 h组电流密度为-(6.59±0.52) pA/pF，较对照组及一次力竭2组下降，且差异有显著性意义(P < 0.01)，反复力竭24 h组电流密度为-(7.01±0.36) pA/pF显著低于对照组及一次力竭0 h组(P < 0.01，P < 0.01，表2)。可见，一次力竭跑台训练并未对大鼠窦房结ICa,T电流产生明显影响，而反复力竭运动则可显著降低大鼠窦房结 I电流密度，这一变化可能导致窦房结细胞去极化初始阶段的Ca2+内流减少，从而减慢动作电位的上升速率，进而可能成为介导运动引起窦房结自律活动减慢的原因之一。Ca,T"

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