Abstract: Objective To observe the impact of alone or combined use of ezetimibe and simvastatin on transient outward potassium current (Ito) in ventricular myocytes of rat model of ischemia and reperfusion (IR). Methods Seventy-five male SD rats were randomly divided into five groups, control group (CON), control-IR group (CIR), ezetimibe treatment group (EIR), simvastatin treatment group (SIR) and combined ezetimibe and simvastatin treatment group (ESIR). After two weeks of treatment with intragastic normal saline or drugs (ezetimibe or simvastatin), myocytes were isolated from right ventricular with collagenase Ⅱ, and Ito was recorded by whole-cell patch clamp technique. Results (1) The Ito current density at +60 mV was significantly decreased in CIR group than that of CON group (P＜0.05). There was no significant difference in Ito current density between SIR group and ESIR group (P＞0.05). The Ito current densities were higher in SIR group and ESIR group compared to those of CIR group. There was no significant difference in Ito current density between SIR group and ESIR group (P＞0.05). (2) There was a significant increase in the half-inactivation (V1/2) in CIR group than that of CON group, but no significant difference between EIR group and CIR group (P > 0.05). There was a significant difference in the half-inactivation (V1/2) in SIR group and ESIR group compared to that of CIR group (P＜0.05), but no significant difference between SIR group and ESIR group (P＞0.05). There was no significant difference in the slope factor (K) between five groups (P＞0.05). (3) The time-constant (τ) of Ito recovery curves from inactivation was significantly higher in CIR group than that of CON group (P＜0.05), which was no significant difference between EIR group and CIR group (P＞0.05). There was a significant difference in the time-constant (τ) of Ito recovery curves from inactivation in SIR group and ESIR group compared to that of CIR group (P＜0.05), but no
significant difference between SIR group and ESIR group (P＞0.05). Conclusion Simvastatin pre-treatment or ezetimibe +simvastatin pre-treatment can reverse the effect of IR on Ito of ventricular myocytes, but ezetimibe shows no such effects.

Key words: patch-clamp techniques, reperfusion injury, Ezetimibe, Simvastatin, transient outward potassium current