Potassium Currents Activated by Depolarization in Odontoblasts

Figures

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  Figure 1. Outwardly rectifying currents in odontoblasts. (A) Representative current traces with extracellular 5 mM [K+]o recorded in Cl−-rich extracellular and intracellular solutions (Cl−-rich ECS and ICS) (middle traces), as well as in gluconate-rich ECS and ICS (Gluc-rich ECS and ICS) (lower traces) are shown. Currents were evoked by 400 ms voltage-steps from −100 to +80 mV in 10 mV increments from a Vh of −70 mV (upper traces). (B) Current-voltage (I-V) relationships for the current recorded in Cl−-rich ECS and ICS (upper), and gluc-rich ECS and ICS (lower) with 5 mM [K+]o (filled squares), 10 mM [K+]o (filled circles), 50 mM [K+]o (open squares), and 100 mM [K+]o (open circles). Each point indicates the current density for the mean ± SD from each of the 6 cell. Statistically significant differences between points at a membrane potential of +80 mV (shown by solid lines) are indicated by asterisks, *P < 0.05.

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  Figure 2. Biophysical properties of outward currents in odontoblasts. (A) Representative current traces recorded under conditions of Cl−-rich ECS and ICS (middle traces) as well as gluc-rich ECS and ICS (lower traces) are shown. Currents were elicited by voltage steps from a Vh of −70 mV to +80 mV before hyperpolarizing in 10 mV increments ranging from −110 to +40 mV (upper traces). To analyze the values of reversal potential, we measured the amplitudes at 50 ms (dashed arrows in both the middle and lower) after initiating hyperpolarized voltage pulsing (dashed double headed arrow in upper) under both conditions. (B) Semilogarithmic plots of reversal potential against various [K+]o (5–100 mM) under Cl−-rich physiological (filled circles) and gluc-rich (open circles) conditions are shown. The reversal potentials under gluc-rich conditions were closely fitted to expected values, which were estimated for pure K+ conductance described by the Nernst equation (solid line). The dashed line shows the reversal potentials estimated by the Goldman-Hodgkin-Katz equation with a Cl− permeability of 0.19 ± 0.16 (K+ permeability was set to 1.0). Each point indicates the reversal potentials for the mean ±…

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  Figure 3. Pharmacological properties of outward currents in odontoblasts. (A) Representative current traces recorded under gluc-rich ECS and ICS conditions without (second upper traces) and with 10 mM TEA (third upper traces), 10 μM 4-AP (forth upper traces), and 100 nM αDTX (bottom traces) are shown. Currents were evoked by 400 ms voltage-steps from −100 to +80 mV in 10 mV increments from a Vh of −70 mV (upper traces). (B) Dose-response relationships between current amplitudes normalized to those without antagonist and those with various concentration of extracellular antagonist: TEA (upper), 4-AP (middle), and αDTX (lower). Each data point was best fitted using Equation 2, and each IC50 value was evaluated. Each point indicates the mean values ± SD from each 6 cell.

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  Figure 4. Effect of K+ channel activity on the mineralization. Photographs show the von Kossa (left panels) and alizarin red (right panels) staining, without (controls; upper panels) or with 2 mM (middle panels) or 4 mM (lower panels) TEA.