A magnesium current in Paramecium.
Recent reappraisals of the role of ionized magnesium in cell function suggest that many cells maintain intracellular free Mg2+ at low concentrations (0.1 to 0.7 mM) and that external agents can influence cell function via changes in intracellular Mg2+ concentration. Depolarization and hyperpolarization of voltage-clamped Paramecium elicited a Mg2(+)-specific current, IMg. Both Co2+ and Mn2+ were able to substitute for Mg2+ as charge carriers, but the resultant currents were reduced compared with Mg2+ currents. Intracellular free Mg2+ concentrations were estimated from the reversal potential of IMg to be about 0.39 mM. The IMg was inhibited when external Ca2+ was removed or a Ca2+ chelator was injected, suggesting that its activation was Ca2(+)-dependent.
Preston
R R
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Laboratory of Molecular Biology, University of Wisconsin-Madison 53706.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004558:Electric Stimulation; D008274:Magnesium / Q000494:pharmacology / Q000502:physiology*; D008345:Manganese / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D010247:Paramecium / Q000187:drug effects / Q000502:physiology*
D008345:Manganese; D008274:Magnesium; D002118:Calcium