Reduction of intracellular Mg2+ caused by reactive oxygen species in rat ventricular myocytes

Author:

Tashiro Michiko1ORCID,Konishi Masato1,Watanabe Makino2,Yokoyama Utako1

Affiliation:

1. Department of Physiology, Tokyo Medical University, Tokyo, Japan

2. Department of Physiology, Faculty of Medicine, Juntendo University, Tokyo, Japan

Abstract

The concentration of intracellular free Mg2+ ([Mg2+]i) should be maintained strictly for the regulation of cellular functions. Since reactive oxygen species (ROS) are liable to increase in various pathological conditions and induce cellular damage, we investigated whether ROS affect intracellular Mg2+ homeostasis. We measured [Mg2+]i in ventricular myocytes from Wistar rats using the fluorescent indicator, mag-fura-2. The administration of hydrogen peroxide (H2O2) decreased [Mg2+]i in Ca2+-free Tyrode’s solution. Intracellular free Mg2+ was also reduced by endogenous ROS as generated by pyocyanin, which was inhibited by pretreatment with n-acetyl cysteine (NAC). The rate of change in [Mg2+]i by 500 μM H2O2 in 5 min (on average, −0.61 μM/s) was independent of extracellular Na+, and intra- and extracellular Mg2+ concentrations. When extracellular Ca2+ was present, the rate of Mg2+ decrease was significantly reduced, on average, by ∼60%. The half-maximal effective concentration of H2O2 on the Mg2+ decrease was estimated to be between 400 and 425 μM. The Mg2+ decrease by H2O2 in the absence of Na+ was inhibited by 200 μM imipramine, a known inhibitor of Na+/Mg2+ exchange. We perfused rat hearts with the Ca2+-free Tyrode’s solution containing H2O2 (500 μM, 5 min) on the Langendorff apparatus,. H2O2 stimulation increased Mg2+ concentration in the perfusate, suggesting the H2O2-induced decrease in [Mg2+]i was caused by Mg2+ extrusion. Collectively, these results suggest the existence of a Na+-independent Mg2+ efflux system activated by ROS in cardiomyocytes. The lower [Mg2+]i may in part be attributed to ROS-mediated cardiac dysfunction.

Funder

MEXT | Japan Society for the Promotion of Science

Publisher

American Physiological Society

Subject

Cell Biology,Physiology

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