{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,2]],"date-time":"2025-11-02T19:22:12Z","timestamp":1762111332708},"reference-count":38,"publisher":"American Physiological Society","issue":"6","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["American Journal of Physiology-Cell Physiology"],"published-print":{"date-parts":[[2000,12,1]]},"abstract":"<jats:p> Cytoplasmic concentration of Mg<jats:sup>2+<\/jats:sup>([Mg<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>) was measured with a fluorescent indicator furaptra in ventricular myocytes enzymatically dissociated from rat hearts (25\u00b0C). To study Mg<jats:sup>2+<\/jats:sup> transport across the cell membrane, cells were treated with ionomycin in Ca<jats:sup>2+<\/jats:sup>-free (0.1 mM EGTA) and high-Mg<jats:sup>2+<\/jats:sup> (10 mM) conditions to facilitate passive Mg<jats:sup>2+<\/jats:sup> influx. Rate of rise of [Mg<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub> due to the net Mg<jats:sup>2+<\/jats:sup>influx was significantly smaller in the presence of 130 mM extracellular Na<jats:sup>+<\/jats:sup> than in its absence. We also tested the extracellular Na<jats:sup>+<\/jats:sup> dependence of the net Mg<jats:sup>2+<\/jats:sup>efflux from cells loaded with Mg<jats:sup>2+<\/jats:sup>. After [Mg<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub> was raised by ionomycin and high Mg<jats:sup>2+<\/jats:sup> to the level 0.5\u20130.6 mM above the basal value (\u223c0.7 mM), washout of ionomycin and lowering extracellular [Mg<jats:sup>2+<\/jats:sup>] to 1.2 mM caused rapid decline of [Mg<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub> in the presence of 140 mM Na<jats:sup>+<\/jats:sup>. This net efflux of Mg<jats:sup>2+<\/jats:sup> was completely inhibited by withdrawal of extracellular Na<jats:sup>+<\/jats:sup> and was largely attenuated by imipramine, a known inhibitor of Na<jats:sup>+<\/jats:sup>\/Mg<jats:sup>2+<\/jats:sup> exchange, with 50% inhibition at 79 \u03bcM. The relation between the rate of net Mg<jats:sup>2+<\/jats:sup> efflux and extracellular Na<jats:sup>+<\/jats:sup> concentration ([Na<jats:sup>+<\/jats:sup>]<jats:sub>o<\/jats:sub>) had a Hill coefficient of 2 and [Na<jats:sup>+<\/jats:sup>]<jats:sub>o<\/jats:sub> at half-maximal rate of 82 mM. These results demonstrate the presence of Na<jats:sup>+<\/jats:sup> gradient-dependent Mg<jats:sup>2+<\/jats:sup> transport, which is consistent with Na<jats:sup>+<\/jats:sup>\/Mg<jats:sup>2+<\/jats:sup> exchange, in cardiac myocytes. <\/jats:p>","DOI":"10.1152\/ajpcell.2000.279.6.c1955","type":"journal-article","created":{"date-parts":[[2017,12,24]],"date-time":"2017-12-24T23:05:08Z","timestamp":1514156708000},"page":"C1955-C1962","source":"Crossref","is-referenced-by-count":18,"title":["Sodium gradient-dependent transport of magnesium in rat ventricular myocytes"],"prefix":"10.1152","volume":"279","author":[{"given":"Michiko","family":"Tashiro","sequence":"first","affiliation":[{"name":"Department of Physiology, The Jikei University School of Medicine, Tokyo 105 - 8461, and"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Masato","family":"Konishi","sequence":"additional","affiliation":[{"name":"Department of Physiology, The Jikei University School of Medicine, Tokyo 105 - 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