Objective    To investigate the modulation of electrophysiological properties of hyperpolarization-activated cyclic nucleotide-gated channels(HCN) HCN1 and HCN2 by transfecting MinK-related peptide 1(MiRP1) in Chinese hamster ovarian (CHO) cells.     Methods    CHO cells were co-transfected with plasmid DNA encoding either of the cardiac HCN isoforms (HCN1

HCN2) with MiRP1 to observe the effect of MiRP1 on HCN whole-cell currents. Whole-cell patch clamp technique was used to record the 2 channel currents of the transfected cells.      Results    MiRP1 significantly increased whole-cell current density of HCN2 [(37.8±4.8) pA/pF（n=11） vs control (25.9±1.7) pA/pF（n=10）; at -140 mV

P0.05]

while not affecting HCN1 current density [(41.3±10.9) pA/pF（n=13） vs control (34.9±7.8) pA/pF（n=11）; P0.05]. Moreover

MiRP1 accelerated the activation kinetic of HCN1 [tau (180.9±8.6) ms vs control (306.1±45.6) ms; at -80 mV

P0.05] and HCN2 [tau (391.8±33.6) ms vs control (763.5±106.1) ms; at -80 mV

P0.05].But MiRP1 did not affect voltage dependence of HCN1 and HCN2 channel activation.     Conclusion    MiRP accelerates HCN1 or HCN2 channel activation kinetics

and leads to increase of HCN2 current density.