Vitamin C Pretreatment Attenuates Hypoxia-induced Disturbance Of Sodium Currents In Guinea-pig Ventricular Myocytes

Objective: To approach the protective mechanisms of vitamin C on hearts during hypoxia, we investigated the electrophysiological effects of vitamin C (1mM, pretreated before hypoxia) on Na+ currents (including the transient Na⁺ current and persistent Na⁺ current) in guinea-pig ventricular myocytes during hypoxia.Methods: The whole-cell and single-channel patch-clamp techniques were used to record I_NaT and I_NaP in isolated ventricular myocytes from guinea pigs.Results: The whole-cell recordings show that the mean current density of I_NaT in hypoxia group decreased from the control value 40.2142±1.7735 to 27.1663±1.8441pA/pF and current density of I_NaP increased from 0.3987±0.0474 to 1.1854±01994pA/pF (n=9, P<0.05 vs. control) at hypoxia 15min. However, when vitamin C was administered before hypoxia as pretreatment, parameters of the I_NaT and I_NaP varied moderately (mean current density of I_NaT decreasing from 41.6038±2.9762 to 34.6341±1.9651pA/pF and current density of I_NaP increasing from 0.3843±0.0636 to 0.6734±0.1057pA/pF, n=9, P<0.05, vs. hypoxia group). Single-channel recordings (cell-patched) show that the mean open probability and open time of I_NaP increased significantly in both groups at hypoxia 15min. However, the increased current values of the hypoxia group were still marked at hypoxia 15min (n=9, P<0.05,vs. vitamin C+ hypoxia group).Conclusion: Our results indicate that vitamin C can attenuate the disturbed effects of hypoxia on Na+ currents ( I_NaT and I_NaP) of cardiac myocytes in guinea-pigs effectively.