力竭运动对大鼠窦房结ATP-敏感型钾离子通道的影响

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。

Effects of Exhaustive Exercise on the ATP-sensitive Potassium Channel in Sinoatrial Node of Rats

Objective This paper discusses the subunit mRNA and current density of ATP-sensitive potassium channel(KATP channel) in sinoatrial node(SAN) at different time phrases after exhaustive exercise.Methods 180 healthy adult male SD rats were equally assigned into 9 groups:1 control group(C),4 single exhaustive swimming groups(O-0hour,O-4hours,O-12hours,O-24hours),and 4 2-week repeated exhaustive swimming groups(R-0hour,R-4hours,R-12hours,R-24hours).Rats swam with 3% of body weight on their tails.2-hour exhaustive swimming was carried out for the repeated swimming groups 6 days per week for a total of 2 weeks.After 2-week normal feeding,2-hour exhaustive swimming was carried out for the single exhaustive swimming groups.The samples of rats were drawn immediately,and at 4,12,and 24 hours after exhaustive swimming from respective groups.The mRNA expression of KATP channel subunit in SAN were analyzed by real-time fluorescent quantitative PCR,and the current density of KATP channel by SAN cells isolation and whole-cell patch clamp analysis.Results(1)The Kir6.2 mRNA expressions of all repeated exhaustive swimming groups were significantly higher than that of control group(P < 0.01).(2)The current density of IK,ATP of the repeated exhaustive swimming groups at all time phrases were significantly higher than that of control group and single exhaustive swimming groups(P < 0.01).Conclusion Exhaustive exercise upregulates the Kir6.2 mRNA subunit expression in SAN,along with the corresponding current IK,ATP,inducing decreased diastolic automatic depolarization and spontaneous activity rate of SAN cells,which probably is one of the most important mechanisms of exercise-induced SAN dysfunction and arrhythmia.