Altered I_f Channel Gene Expression in Mouse Hearts after Myocardial Infarction

If channels play a key role in the pacemaker activity of sinus node in adult heart. Four subtypes of (HCN1-4), which encode If channel, have been identified. In the present study, we quantitatively estimated the expression of HCN1-4 mRNA in mouse ventricular myocardium 4 weeks after myocardial infarction (MI) by a real time PCR. In sham-operated control mice, HCN2 mRNA was expressed most abundantly (915.2′225.0molecules / 10 5 GAPDH molecules) in the ventricle. The expressions of mRNAs for HCN1, HCN3 and HCN4 were less abundant (15.2′5.0, 9.7′1.1, 48.2′25.3 molecules / 10 5 GAPDH molecules respectively). In mice after MI, HCN2 mRNA increased significantly by 2.7 fold compared to controls. There was no significant difference of HCN1, HCN3 and HCN4 mRNA between two groups. There is an upregulation of HCN2 mRNA in compensated hypertrophied muscle in MI. This might be responsible for an enhancement of abnormal automaticity in the hearts after MI.