Effect of hydrogen peroxide on persistent sodium current in guinea pig ventricular myocytes.

AIM: To study the effect of hydrogen peroxide (H2O2) on persistent sodium current (I(Na.P)) in guinea pig ventricular myocytes.
METHODS: The whole-cell, cell-attached, and inside-out patch-clamp techniques were applied on isolated ventricular myocytes from guinea pig.
RESULTS: H2O2 (0.1 mmol/L, 0.5 mmol/L and 1.0 mmol/L) increased the amplitude of whole-cell I(Na.P) in a concentration-dependent manner, and glutathione (GSH 1 mmol/L) reversed the increased I(Na.P). H2O2 (1 mmol/L) increased persistent sodium channel activity in cell-attached and inside-out patches. The mean open probability was increased from control values of 0.015+/-0.004 and 0.012+/-0.003 to 0.106+/-0.011 and 0.136+/-0.010, respectively (P< 0.01 vs control). They were then decreased to 0.039+/-0.024 and 0.027+/-0.006, respectively, after the addition of 1 mmol/L GSH (P<0.01 vs H2O2). The time when open probability began to increase and reached a maximum was shorter in inside-out patches than that in cell-attached patches (4.8+/-1.0 min vs 11.5+/-3.9 min, P<0.01; 9.6+/-1.6 min vs 18.7+/-4.7 min, P<0.01).
CONCLUSION: H2O2 increased the I(Na.P) of guinea pig ventricular myocytes in a concentration-dependent manner, possibly by directly oxidating the cell membrane.