力竭运动对大鼠窦房结超级化激活环核苷酸门控通道的影响

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。

Effects of Exhaustive Exercise on the Hyperpolarization-activated Cyclic Nucleotide-gated Channels in Sinoatrial Node of Rat

Objective This paper discusses the subunit mRNA and current density of hyperpolarization-activated cyclic nucleotide-gated channels(HCN channel) in sinoatrial node(SAN) at different time phrases after exhaustive exercise.Methods 180 healthy adult male SD rats were equally assigned into following 9 groups:1 control groups(C),4 single bout of exhaustive swimming groups(O),and 4 2-week repeated exhaustive swimming groups(R).2-hour exhaustive swimming with 3% of body weight on their tails was carried out for groups R,6 days per week for a total of 2 weeks.After 2-week normal feeding,The same exhaustive swimming as for groups R was carried out for the groups O.The samples were drawn immediately,and at 4,12,and 24 hours after exhaustive swimming.The mRNA expression of HCN channel subunits in SAN in groups R were analyzed by real-time fluorescent quantitative PCR,and the current density of HCN channel by SAN cells isolation and whole-cell patch clamp.Results(1)The HCN1 and HCN4 mRNA expressions in group O immediate(P < 0.05,P < 0.01),especially 4 hours after swimming(P < 0.01,P < 0.05) were significantly higher than that in group C,and HCN2 and HCN4 mRNA expressions in groups R immediate and 4 hours after swimming were significantly lower than that in group C(P < 0.01,P < 0.01).The HCN2 and HCN4 mRNA expressions in group R 4,12,and 24 hours after exhaustive swimming decreased significantly(P < 0.01).(2)The current density of HCN channel in group R 4,12,and 24 hours after exhaustive swimming were significantly lower than that in group C and in group O 4,12,and 24 hours after exhaustive swimming(P < 0.01).Conclusion Exhaustive exercise downregulated the SAN HCN2 and HCN4 mRNA expressions,along with the corresponding current If,and induced remolding of HCN channel,which could be one of the most important factors of exercise-induced sinoatrial node dysfunction.