Abstract: AIM: To determine the effect and mechanism of H₂O₂ on L-type calcium current (ICa, L) in single rat verntricular myocyte.METHODS: Whole-cell pacthclamp recording technique was used to record ICa, L in single cells isolated rat ventricular myocytes.RESULTS: The nifedipine-sensitive L-type calcium inward current was recorded in the rat ventricular myocytes.5 mmol·L^-1 H₂O₂ increased the calcium channel current in a voltagedependent manner in ventricular myocytes of rats.The current-voltage curvewas shifted downwards, which active potential, peak potential and reverse potential had no significant changes.The time constants for inactivation (τ) are significantly greater (P <0.01) in the absence than the presence of 5 mmol·L^-1 H₂O₂ over the entire range investigated, but its time constants for activation (τ) had no significant differences.The inactivation curve was shifted to more negative potential, but the activation curve was not altered.CONCLUSION: H₂O₂ can increase calcium channel current and slow channel inactivation in ventricular myocytes of rats.

Key words: H₂O₂, L-type calcium channel current, ventricular myocytes, whole-cell patch-clamp recording technique