{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,16]],"date-time":"2026-03-16T11:27:39Z","timestamp":1773660459427,"version":"3.50.1"},"reference-count":50,"publisher":"American Physiological Society","issue":"1","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Neurophysiology"],"published-print":{"date-parts":[[2005,7]]},"abstract":"<jats:p>Mg<jats:sup>2+<\/jats:sup>-extrusion from Mg<jats:sup>2+<\/jats:sup>-loaded neurons of the leech, Hirudo medicinalis, is mediated mainly by Na<jats:sup>+<\/jats:sup>\/Mg<jats:sup>2+<\/jats:sup>antiport. However, in a number of leech neurons, Mg<jats:sup>2+<\/jats:sup>is extruded in the nominal absence of extracellular Na<jats:sup>+<\/jats:sup>, indicating the existence of an additional, Na<jats:sup>+<\/jats:sup>-independent Mg<jats:sup>2+<\/jats:sup>transport mechanism. This mechanism was investigated using electrophysiological and microfluorimetrical techniques. The rate of Na<jats:sup>+<\/jats:sup>-independent Mg<jats:sup>2+<\/jats:sup>extrusion from Mg<jats:sup>2+<\/jats:sup>-loaded leech neurons was found to be independent of extracellular Ca<jats:sup>2+<\/jats:sup>, K<jats:sup>+<\/jats:sup>, NO<jats:sub>3<\/jats:sub><jats:sup>\u2212<\/jats:sup>, HCO<jats:sub>3<\/jats:sub><jats:sup>\u2212<\/jats:sup>, SO<jats:sub>4<\/jats:sub><jats:sup>2\u2212<\/jats:sup>, HPO<jats:sub>4<\/jats:sub><jats:sup>2\u2212<\/jats:sup>, and of intra- and extracellular pH. Na<jats:sup>+<\/jats:sup>-independent Mg<jats:sup>2+<\/jats:sup>extrusion was not inhibited by 4,4\u2032-diisothiocyanatostilbene-2,2\u2032-disulfonic acid (DIDS), furosemide, ouabain, vanadate, iodoacetate, 4-amino-hippurate, or \u03b1-cyano-4-hydroxycinnamate and was not influenced by changes in the membrane potential in voltage-clamp experiments. Na<jats:sup>+<\/jats:sup>-independent Mg<jats:sup>2+<\/jats:sup>extrusion was, however, inhibited by the application of 2 mM probenecid, a blocker of organic anion transporters, suggesting that Mg<jats:sup>2+<\/jats:sup>might be co-transported with organic anions. Extracellularly, of all organic anions tested (malate, citrate, lactate, \u03b1-ketoglutarate, and 4-amino-hippurate) only high, but physiological, concentrations of malate (30 mM) had a significant inhibitory effect on Na<jats:sup>+<\/jats:sup>-independent Mg<jats:sup>2+<\/jats:sup>extrusion. Intracellularly, iontophoretically injected malate, citrate, or fura-2, but not Cl<jats:sup>\u2212<\/jats:sup>, \u03b1-ketoglutarate, glutamate, succinate, or urate, were stimulating Na<jats:sup>+<\/jats:sup>-independent Mg<jats:sup>2+<\/jats:sup>extrusion from those neurons that initially did not extrude Mg<jats:sup>2+<\/jats:sup>in Na<jats:sup>+<\/jats:sup>-free solutions. Our data indicate that Mg<jats:sup>2+<\/jats:sup>is co-transported with organic anions, preferably with malate, the predominant extracellular anion in the leech. The proposed model implies that, under experimental conditions, malate drives Mg<jats:sup>2+<\/jats:sup>extrusion, whereas under physiological conditions, malate is actively taken up, driven by Mg<jats:sup>2+<\/jats:sup>, so that malate can be metabolized.<\/jats:p>","DOI":"10.1152\/jn.01221.2004","type":"journal-article","created":{"date-parts":[[2005,3,24]],"date-time":"2005-03-24T02:30:36Z","timestamp":1111631436000},"page":"441-453","source":"Crossref","is-referenced-by-count":2,"title":["Mg<sup>2+<\/sup>-Malate Co-Transport, a Mechanism for Na<sup>+<\/sup>-Independent Mg<sup>2+<\/sup>Transport in Neurons of the Leech<i>Hirudo medicinalis<\/i>"],"prefix":"10.1152","volume":"94","author":[{"given":"Dorothee","family":"G\u00fcnzel","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Karin","family":"Hintz","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Simone","family":"Durry","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wolf-R\u00fcdiger","family":"Schlue","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"24","reference":[{"key":"R1","doi-asserted-by":"crossref","unstructured":"Ammann D.Ion-Selective Microelectrodes. 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