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目的:探讨两周力竭运动对大鼠窦房结ATP-敏感型钾离子通道(KATP通道)亚基Kir6.2mRNA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、反复力竭组(R组)4组。安静对照组不进行任何运动。反复力竭组大鼠尾部负重3%体重,每天进行1次力竭游泳,每次约2小时,每周6天,共运动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,一次力竭运动各组大鼠分别以O-0h、O-4h、O-12h、O-24h命名,反复力竭运动各组大鼠分别以R-0h、R-4h、R-12h、R-24h命名,应用实时荧光定量PCR技术测定KATP通道亚基Kir6.2 mRNA表达变化,应用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,以观察力竭游泳运动对大鼠窦房结细胞膜上KATP通道的影响。结果:反复力竭运动各组Kir6.2 mRNA表达显著高于对照组(P<0.01)。反复力竭各时相组KATP通道IK,ATP电流密度显著高于对照组及一次力竭组(P<0.01)。结论:反复力竭运动可引起窦房结细胞膜KATP通道亚基Kir6.2 mRNA表达及IK,ATP电流密度增加,这可能引起窦房结细胞舒张期自动除极及自律活动减慢,提示反复力竭运动对于KATP通道的影响可能成为运动引发窦房结功能障碍及运动性心律失常的离子通道机制之一。
Objective: To investigate the effects of exhaustive exercise for two weeks on Kir6.2 mRNA expression and channel current density of ATP-sensitive potassium channel (KATP channel) subunit 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, repeated exhaustive group (R group) 4 groups. Quiet control group did not exercise. Rats in repeated exhaustive group weighed 3% of body weight, and exhausted swimming was performed once a day for about 2 hours and 6 days a week for a total of 2 weeks. An exhaustive group of rats in an exhaustive swimming exercise after 2 weeks of normal feeding, exercise program with repeated exhaustion group. Rats in exercise group were drawn at different time points immediately after exercise, 4 hours, 12 hours and 24 hours respectively. Rats in one exhaustive exercise group were named as O-0h, O-4h, O-12h and O-24h, The rats in repeated exhaustive exercises were named R-0h, R-4h, R-12h and R-24h respectively. Kir6.2 mRNA expression of KATP channel subunit was determined by real-time fluorescence quantitative PCR. Whole-cell patch-clamp technique was used to determine the change of channel current density in order to observe the effects of exhaustive swimming on KATP channel in rat sinoatrial cell membrane. Results: Kir6.2 mRNA expression was significantly higher in each group than in exhaustive exercise group (P <0.01). The IK and ATP current densities of KATP channel in each phase group were significantly higher than those in control group and exhaustive group (P <0.01). CONCLUSION: Repeated exhaustive exercise induces Kir6.2 mRNA expression and increase of IK and ATP current density in sarcoplasmic cell membrane of sinoatrial node cells, which may lead to the slow release of diastolic auto-depolarization and autonomic activity of sinoatrial node cells, suggesting that the repetitive force The effect of exhaustive exercise on KATP channels may be one of the ion channel mechanisms for exercise-induced sinus node dysfunction and arrhythmia.