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Mercury (Hg2+) and zinc (Zn2+): Two divalent cations with different actions on voltage-activated calcium channel currents

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Summary

1. We examined the actions of mercury (Hg2+) and zinc (Zn2+) on voltage-activated calcium channel currents of cultured rat dorsal root ganglion (DRG) neurons, using the whole-cell patch clamp technique.

2. Micromolar concentrations of both cations reduced voltage-activated calcium channel currents. Calcium channel currents elicited by voltage jumps from a holding potential of −80 to 0 mV (mainly L- and N-currents) were reduced by Hg2+ and Zn2+. The threshold concentration for Hg2+ effects was 0.1 µM and that for Zn2+ was 10µM. Voltage-activated calcium channel currents were abolished (>80%) with 5µM Hg2+ or 200µM Zn2+. The peak calcium current was reduced to 50% (IC50) by 1.1µM Hg2+ or 69µM Zn2+. While Zn2+ was much more effective in reducing the T-type calcium channel current—activated by jumping from −80 to −35 mV—Hg2+ showed some increased effectiveness in reducing this current.

3. The effects of both cations occurred rapidly and a steady state was reached within 1–3 min. While the action of Zn2+ was not dependent on an open channel state, Hg2+ effects depended partially on channel activation.

4. While both metal cations reduced the calcium channel currents over the whole voltage range, some charge screening effects were detected with Hg2+ and with higher concentrations (>100µM) of Zn2+.

5. As Zn2+ in the concentration range used had no influence on resting membrane currents, Hg2+ caused a clear inward current at concentrations ⩾µM.

6. In the present study we discuss whether the actions of both metals on voltage-activated calcium channel currents are mediated through the same binding site and how they may be related to their neurotoxic effects.

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  1. Heinrich-Heine Universität Düsseldorf, Physiologie II, Moorenstraße 5, D-40225, Düsseldorf, Germany

    D. Büsselberg, M. Pekel, D. Michael & B. Platt

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  1. D. Büsselberg
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  4. B. Platt
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Büsselberg, D., Pekel, M., Michael, D. et al. Mercury (Hg2+) and zinc (Zn2+): Two divalent cations with different actions on voltage-activated calcium channel currents. Cell Mol Neurobiol 14, 675–687 (1994). https://doi.org/10.1007/BF02088676

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