The Journal of Physiological Sciences

, Volume 69, Issue 1, pp 97–102 | Cite as

Modulation of Mg2+ influx and cytoplasmic free Mg2+ concentration in rat ventricular myocytes

  • Michiko TashiroEmail author
  • Hana Inoue
  • Masato Konishi
Original Paper


To examine whether TRPM7, a member of the melastatin family of transient receptor potential channels, is a physiological pathway for Mg2+ entry in mammalian cells, we studied the effect of TRPM7 regulators on cytoplasmic free Mg2+ concentration ([Mg2+]i) of rat ventricular myocytes. Acutely isolated single cells were AM-loaded with the fluorescent indicator furaptra, and [Mg2+]i was estimated at 25 °C. After [Mg2+]i was lowered by soaking the cells with a high-K+ and Mg2+-Ca2+-free solution, [Mg2+]i was recovered by extracellular perfusion of Ca2+-free Tyrode’s solution that contained 1 mM Mg2+. The initial rate of increase in [Mg2+]i was analyzed as the Mg2+ influx rate. The Mg2+ influx rate was increased by the TRPM7 activator, naltriben (2–50 μM), in a concentration-dependent manner with a half maximal effective concentration (EC50) of 24 μM. This EC50 value is similar to that reported for the activation of recombinant TRPM7 overexpressed in HEK293 cells. Naltriben (50 μM) caused little change in basal [Mg2+]i (~ 0.9 mM) in Ca2+-free Tyrode’s solution, but significantly raised [Mg2+]i to 1.31 ± 0.03 mM in 94 min after the removal of extracellular Na+. Re-introduction of extracellular Na+ lowered [Mg2+]i back to the basal level even in the presence of naltriben. Application of 10 μM NS8593, an inhibitor of TRPM7, significantly lowered [Mg2+]i to 0.72 ± 0.03 mM in 50-60 min independent of extracellular Na+. The results suggest that Mg2+ entry through TRPM7 significantly contributes to physiological Mg2+ homeostasis in mammalian heart cells.


Magnesium influx TRPM7 Naltriben NS8593 Rat ventricular myocyte 



We thank Shinobu Tai for technical assistance and Mary Shibuya for reading the manuscript. This work was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number JP15K08188, and the Institute of Seizon and Life Sciences.

Authors’ contributions

All authors conceived and designed the study. MT performed the experiments, analyzed data, and wrote the initial draft of the manuscript. MK contributed to analysis and interpretation of data, and wrote the manuscript. HI contributed to data interpretation, and critically reviewed the manuscript. All authors approved the final version of the manuscript.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


  1. 1.
    Monteilh-Zoller MK, Hermosura MC, Nadler MJ, Scharenberg AM, Penner R, Fleig A (2003) TRPM7 provides an ion channel mechanism for cellular entry of trace metal ions. J Gen Physiol 121:49–60CrossRefGoogle Scholar
  2. 2.
    Nadler MJ, Hermosura MC, Inabe K, Perraud AL, Zhu Q, Stokes AJ, Kurosaki T, Kinet JP, Penner R, Scharenberg AM, Fleig A (2001) LTRPC7 is a Mg.ATP-regulated divalent cation channel required for cell viability. Nature 411:590–595. CrossRefGoogle Scholar
  3. 3.
    Carter RN, Tolhurst G, Walmsley G, Vizuete-Forster M, Miller N, Mahaut-Smith MP (2006) Molecular and electrophysiological characterization of transient receptor potential ion channels in the primary murine megakaryocyte. J Physiol 576:151–162. CrossRefGoogle Scholar
  4. 4.
    Abed E, Labelle D, Martineau C, Loghin A, Moreau R (2009) Expression of transient receptor potential (TRP) channels in human and murine osteoblast-like cells. Mol Membr Biol 26:146–158. CrossRefGoogle Scholar
  5. 5.
    Wei WL, Sun HS, Olah ME, Sun X, Czerwinska E, Czerwinski W, Mori Y, Orser BA, Xiong ZG, Jackson MF, Tymianski M, MacDonald JF (2007) TRPM7 channels in hippocampal neurons detect levels of extracellular divalent cations. Proc Natl Acad Sci USA 104:16323–16328. CrossRefGoogle Scholar
  6. 6.
    Prakriya M, Lewis RS (2002) Separation and characterization of currents through store-operated CRAC channels and Mg2+-inhibited cation (MIC) channels. J Gen Physiol 119:487–507CrossRefGoogle Scholar
  7. 7.
    Kozak JA, Kerschbaum HH, Cahalan MD (2002) Distinct properties of CRAC and MIC channels in RBL cells. J Gen Physiol 120:221–235CrossRefGoogle Scholar
  8. 8.
    Chubanov V, Schnitzler Mederos Y, Meißner M, Schäfer S, Abstiens K, Hofmann T, Gudermann T (2012) Natural and synthetic modulators of SK (K(ca) 2) potassium channels inhibit magnesium-dependent activity of the kinase-coupled cation channel TRPM7. Br J Pharmacol 166:1357–1376. CrossRefGoogle Scholar
  9. 9.
    Tashiro M, Inoue H, Konishi M (2014) Physiological pathway of magnesium influx in rat ventricular myocytes. Biophys J 107:2049–2058. CrossRefGoogle Scholar
  10. 10.
    Hofmann T, Schäfer S, Linseisen M, Sytik L, Gudermann T, Chubanov V (2014) Activation of TRPM7 channels by small molecules under physiological conditions. Pflugers Arch 466:2177–2189. CrossRefGoogle Scholar
  11. 11.
    Tashiro M, Inoue H, Tai S, Konishi M (2018) Activation of the TRPM7 channel raises basal [Mg2+]i only in the absence of extracellular Na+. J Physiol Sci S74Google Scholar
  12. 12.
    Tursun P, Tashiro M, Konishi M (2005) Modulation of Mg2+ efflux from rat ventricular myocytes studied with the fluorescent indicator furaptra. Biophys J 88:1911–1924CrossRefGoogle Scholar
  13. 13.
    Hongo K, Konishi M, Kurihara S (1994) Cytoplasmic free Mg2+ in rat ventricular myocytes studied with the fluorescent indicator furaptra. Jpn J Physiol 44:357–378CrossRefGoogle Scholar
  14. 14.
    Watanabe M, Konishi M (2001) Intracellular calibration of the fluorescent Mg2+ indicator furaptra in rat ventricular myocytes. Pflugers Arch 442:35–40CrossRefGoogle Scholar
  15. 15.
    Tashiro M, Inoue H, Konishi M (2010) KB-R7943 inhibits Na+-dependent Mg2+ efflux in rat ventricular myocytes. J Physiol Sci 60:415–424. CrossRefGoogle Scholar
  16. 16.
    Tashiro M, Konishi M (2000) Sodium gradient-dependent transport of magnesium in rat ventricular myocytes. Am J Physiol Cell Physiol 279:C1955–C1962CrossRefGoogle Scholar
  17. 17.
    Tashiro M, Tursun P, Konishi M (2005) Intracellular and extracellular concentrations of Na+ modulate Mg2+ transport in rat ventricular myocytes. Biophys J 89:3235–3247CrossRefGoogle Scholar

Copyright information

© The Physiological Society of Japan and Springer Japan KK, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of PhysiologyTokyo Medical UniversityTokyoJapan

Personalised recommendations