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目的:探讨2周力竭运动对大鼠窦房结超级化激活环核苷酸门控通道亚基HCN1、HCN2、HCN4 mRNA表达及通道电流密度的影响。方法:健康雄性SD大鼠180只,8周龄,体重(220±8)g,共分9组,每组20只,包括安静对照组(C组)1组、一次力竭组(O组)4组和反复力竭组(R组)4组。安静对照组不施加任何运动影响,反复力竭各组大鼠尾部负重为体重的3%,每天1次力竭游泳,每次运动时间控制在2小时左右,每周运动6天,共2周,一次力竭组大鼠在正常喂养2周后进行一次力竭游泳运动,运动方案同反复力竭组。运动组大鼠分别于运动后即刻、4小时、12小时、24小时不同时相取材,一次力竭运动各组分别命名O-0h、O-4h、O-12h、O-24h,反复力竭运动各组分别命名R-0h、R-4h、R-12h、R-24h。应用实时荧光定量PCR技术测定HCN通道亚基HCN1、HCN2、HCN4 mRNA表达变化,细胞急性分离及全细胞膜片钳技术测定通道电流密度变化,观察力竭游泳运动对大鼠窦房结细胞膜上HCN通道的影响。结果:(1)与对照组相比,一次力竭组O-0h组HCN1、HCN4 mRNA相对表达量显著升高(P<0.05,P<0.01),O-4h组HCN1、HCN4显著升高(P<0.01,P<0.05);反复力竭组R-0h与R-4h组HCN1显著下降(P<0.01,P<0.01);反复力竭各组HCN2、HCN4 mRNA表达显著下降(P<0.01)。(2)反复力竭各时相组HCN通道电流密度显著低于对照组及一次力竭组。结论:两周力竭运动可引起窦房结HCN通道亚基HCN2及HCN4 mRNA表达下降,通道If电流密度减少,这可能成为运动引发窦房结功能障碍的离子通道机制之一。
OBJECTIVE: To investigate the effect of 2-week exhaustive exercise on the expression of HCN1, HCN2 and HCN4 mRNA and the channel current density in the supernuclear activated caspase-mediated subunits of rat sinoatrial node. METHODS: One hundred and eighty healthy male Sprague-Dawley rats, 8 weeks old and 220 ± 8 g body weight, were divided into 9 groups (n = 20 each), including 1 group of quiet control group (C group) ) 4 groups and repeated exhaustive group (R group) 4 groups. Quiet control group without any exertion of exercise, repeated exhaustive tail of rats in each group weight of 3% of body weight, 1 day of exhaustive swimming, each exercise time control in about 2 hours, exercise 6 days a week for 2 weeks One exhaustive group rats were subjected to an exhaustive swimming exercise after two weeks of normal feeding. The exercise program was repeated with exhaustive group. The rats in the exercise group were taken at different time points immediately after exercise, 4 hours, 12 hours and 24 hours respectively. Each group was named as O-0h, O-4h, O-12h, O-24h after exhaustive exercise, Exercise groups were named R-0h, R-4h, R-12h, R-24h. The changes of mRNA expression of HCN1, HCN2 and HCN4 in HCN channel were measured by real-time fluorescence quantitative PCR. The changes of current density were measured by acute cell separation and whole-cell patch clamp technique. The effects of exhaustive swimming on HCN channel Impact. Results: (1) Compared with the control group, the relative expression of HCN1 and HCN4 mRNA in O-0h group was significantly increased (P <0.05, P <0.01), and the levels of HCN1 and HCN4 in O-4h group were significantly increased (P <0.01, P <0.05). HCN1 expression in R-0h and R-4h groups was significantly decreased (P <0.01, P <0.01) ). (2) The current densities of HCN channel in each phase group were significantly lower than those in control group and exhaustive group. CONCLUSION: Exhaustive exercise for two weeks can induce the decrease of HCN2 and HCN4 mRNA expression in the sinus node, and decrease the current density of If in the sinus node, which may be one of the ion channel mechanisms of exercise-induced sinus node dysfunction.