Hg(2+) affects the intracellular free Ca(2+) oscillatory pattern and the correlated membrane conductance changes in Mg(2+)-stimulated oocytes of the prawn Palaemon serratus

J Exp Zool. 2002 Jun 15;293(1):1-11. doi: 10.1002/jez.10112.

Abstract

The impact of mercuric ions (Hg(2+)) on prawn oocytes was examined. Prawn oocytes constitute an unusual system in that they are activated at spawning by seawater Mg(2+), which mediates correlated dynamic changes in intracellular free calcium concentration [(Ca(2+))(i)] and membrane conductance associated with the meiosis resumption. Using a voltage clamp technique and intracellular calcium measurements, we observed that treatment with Hg(2+) (5, 10, and 20 microM) resulted in simultaneous impairments of both (Ca(2+))(i) and membrane current responses to external Mg(2+). Treatment with Hg(2+) also resulted in a gradual dose-dependent slow increase in the baseline level of both (Ca(2+))(i) and membrane conductance, independent of stimulation with external Mg(2+). The effect of Hg(2+) on (Ca(2+))(i) and membrane conductance changes resulted from a block of the signal transduction pathway at some point before the InsP(3) receptor channel involved in Ca(2+) release from the endoplasmic reticulum (ER) stocks. The Hg(2+)-dependent gradual increase in both (Ca(2+))(i) and membrane conductance baseline levels may potentially result from a slow permeabilization of the ER membrane, resulting in Ca(2+) leaking into the cytosol. Indeed, this effect could be blocked with the cell permeable Hg(2+) competitor dithiothreitol, which was able to displace Hg(2+) from its intracellular target regardless of whether external Ca(2+) was present or not.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium / pharmacology
  • Cell Membrane / drug effects
  • Dithiothreitol / pharmacology
  • Electric Conductivity
  • Endoplasmic Reticulum / drug effects
  • Endoplasmic Reticulum / metabolism
  • Ion Channels / drug effects
  • Ion Channels / metabolism
  • Magnesium / antagonists & inhibitors
  • Magnesium / pharmacology*
  • Meiosis / drug effects
  • Membrane Potentials / drug effects*
  • Mercury / pharmacology*
  • Oocytes / drug effects*
  • Oocytes / metabolism
  • Palaemonidae / cytology*
  • Permeability / drug effects
  • Seawater
  • Signal Transduction / drug effects

Substances

  • Ion Channels
  • Mercury
  • Magnesium
  • Calcium
  • Dithiothreitol