Reversible Oxidation ofMyometrial Voltage-Gated Potassium Channels with Hydrogen Peroxide

The uteri, spontaneously active or Ca2+ (6mM) induced, were allowed to equilibrate, and to inhibit voltage-gated potassium (KV ) channels 1mM4-amino pyridine (4-AP) was applied for 15 min before addingH2O2 . H2O2 was added cumulatively: 2 μM, 20 μM, 200 μM, 400 μM, and 3mM. Average time for H2O2 concentrations (2, 20, 200, and 400) μM to reach its full effect was 15 min. H2O2 3mMhad a prolonged effect and therefore was left to act for 30 min. Two-way ANOVA showed significant differences in time dependency between spontaneous and Ca2+-induced rat uteri after applying 3mMH2O2 (type of contraction, P = 0.0280), but not 400 μMH2O2 (P = 0.9271). Our results indicate that H2O2 oxidises channel intracellular thiol groups and activates the channel, inducing relaxation. Cell antioxidative defence system quickly activates glutathione peroxidase (GSHPx) defence mechanism but not catalase (CAT) defence mechanism. Intracellular redox mechanisms repair the oxidised sites and again establish deactivation of KV channels, recuperating contractility. In conclusion, our results demonstrate that KV channels can be altered in a timedependent manner by reversible redox-dependent intracellular alterations.
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