Effects Of Exhaustive Exercise On HCN Channels Of Rat Cardiacconduction System

Abstract

PURPOSE: To study the subunit and current density of Hyperpolarization-activated cyclic nucleotide-gated channels(HCN channels)of sinoatrial node(SAN) at different time phrases after exhaustive exercise and explore whether cardiac conduction system is involved in the exercise-induced cardiac injury. METHODS: 180 healthy adult male SD rats were equally assigned into 9 groups,including 1 control groups, 4 groups undergoing single exhaustive swimming(O group), and 4 groups undergoing 2-week repeated exhaustive swimming(R group). The samples were drawn from rats immediately,and at 4, 12, and 24 hours after exhaustive swimming. The mRNA expression of HCN channel subunit in SAN were analyzed by real-time fluorescent quantitative PCR, current density of SAN HCN channels were analyzed by whole-cell patch clamp analysis. RESULTS: (1)The HCN1and HCN 4 mRNA expression of the single exhaustive swimming group O-0h were significantly higher than that of control group(P <0.05, P <0.01);the HCN2 and HCN 4 mRNA expression of the repeated exhaustive swimming group at 4 time phrases were significantly lower than that of control group(P <0.01).(2)The current density of HCN channel of the repeated exhaustive swimming group at 4 time phrases were significantly lower than that of control group and single exhaustive swimming group(P < 0.01). CONCLUSIONS: The study suggeste exhaustive exercise down-regulating the SAN HCN2 ang HCN 4 mRNA expression, along with the corresponding current If. The exhaustive exercise induced remolding of HCN channel may be an important mechanism of exercise-induced sinoatrial node dysfunction.