Ionized magnesium in the homeostasis of cells

Intracellular threshold for Mg2+ in human platelets

Anthony Okorodudu, Huiwu Yang, M. Tarek Elghetany

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The role of extracellular magnesium ions in the homeostasis of intracellular ionized magnesium ([Mg2+]i) in human platelets was studied. For media containing 0.00 to 0.60 mmol/l of extracellular ionized magnesium ([Mg2+]o), the mean [Mg2+]i fluctuated between 533 and 760 μmol/l. As the [Mg2+]o was increased to 1.5 mmol/l, the [Mg2+]i increased proportionately and peaked at 1470.1 μmol/l. Additional increase in the [Mg2+]o from 1.50 to 6.00 mmol/l resulted in decreased [Mg2+]i until it equilibrated between 739 and 776 μmol/l. The influx of Mg2+ at [Mg2+]o of 0.60 and 1.50 mmol/l was studied using verapamil, a calcium channel inhibitor, and ouabain, an inhibitor of the Na/K pump, respectively. The verapamil (25 mmol/l) blocking experiments resulted in a 92.4% inhibition of the Mg2+ influx into the platelet at a [Mg2+]o of 1.50 mmol/l. Ouabain (0.5 and 2.5 mmol/l) showed an enhancement effect on the influx of Mg2+ at [Mg2+]o of 0.60 mmol/l and no effect at 1.50 mmol/l. The effect of verapamil indicates that ion channels that are homologous to calcium ion channels may be involved in the influx of Mg2+ into the platelets. The inhibition of Mg2+ influx for [Mg2+]o greater than 1.50 mmol/l may illustrate a protective mechanism that attempts to maintain the viability of platelets at abnormally high [Mg2+]o. These results suggest that there is an intracellular Mg2+ threshold of 1500 μmol/l, above which an active mechanism prevents further influx of Mg2+.

Original languageEnglish (US)
Pages (from-to)147-154
Number of pages8
JournalClinica Chimica Acta
Volume303
Issue number1-2
DOIs
StatePublished - 2001

Fingerprint

Platelets
Magnesium
Homeostasis
Blood Platelets
Verapamil
Ouabain
Calcium Channels
Ion Channels
Pumps
Ions
Experiments

Keywords

  • Cytosolic free magnesium
  • Ion channel blockers
  • Mg transport
  • Threshold for intracellular ionized magnesium

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry

Cite this

Ionized magnesium in the homeostasis of cells : Intracellular threshold for Mg2+ in human platelets. / Okorodudu, Anthony; Yang, Huiwu; Tarek Elghetany, M.

In: Clinica Chimica Acta, Vol. 303, No. 1-2, 2001, p. 147-154.

Research output: Contribution to journalArticle

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abstract = "The role of extracellular magnesium ions in the homeostasis of intracellular ionized magnesium ([Mg2+]i) in human platelets was studied. For media containing 0.00 to 0.60 mmol/l of extracellular ionized magnesium ([Mg2+]o), the mean [Mg2+]i fluctuated between 533 and 760 μmol/l. As the [Mg2+]o was increased to 1.5 mmol/l, the [Mg2+]i increased proportionately and peaked at 1470.1 μmol/l. Additional increase in the [Mg2+]o from 1.50 to 6.00 mmol/l resulted in decreased [Mg2+]i until it equilibrated between 739 and 776 μmol/l. The influx of Mg2+ at [Mg2+]o of 0.60 and 1.50 mmol/l was studied using verapamil, a calcium channel inhibitor, and ouabain, an inhibitor of the Na/K pump, respectively. The verapamil (25 mmol/l) blocking experiments resulted in a 92.4{\%} inhibition of the Mg2+ influx into the platelet at a [Mg2+]o of 1.50 mmol/l. Ouabain (0.5 and 2.5 mmol/l) showed an enhancement effect on the influx of Mg2+ at [Mg2+]o of 0.60 mmol/l and no effect at 1.50 mmol/l. The effect of verapamil indicates that ion channels that are homologous to calcium ion channels may be involved in the influx of Mg2+ into the platelets. The inhibition of Mg2+ influx for [Mg2+]o greater than 1.50 mmol/l may illustrate a protective mechanism that attempts to maintain the viability of platelets at abnormally high [Mg2+]o. These results suggest that there is an intracellular Mg2+ threshold of 1500 μmol/l, above which an active mechanism prevents further influx of Mg2+.",
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