Reversibility of Na+/Mg2+ antiport in rat erythrocytes.
Rat erythrocytes loaded with Mg2+ plus Na+ performed Mg2+ uptake under an intracellular/extracellular Na+ gradient. Mg2+ uptake was coupled to Na+ release at a stoichiometric ratio of 1 Mg2+/2 Na+.Mg2+ uptake was inhibited by amiloride, imipramine and quinidine. Mn2+ was taken up by the same transporter as Mg2+. Similar results had been found for net Mg2+ efflux via Na+/Mg2+ antiport in such rat erythrocytes. Hence, it can be concluded that Na+/Mg2+ antiport in Mg(2+)-loaded rat erythrocytes operates reversibly according to the direction of the Na+ gradient which is a contributing driving force. Net Mg2+ influx was dependent on ATP which increased the affinity of intracellular Mg2+ by activating Na+/Mg2+ antiport. Mg2+ uptake was increased by phorbol ester and inhibited by staurosporine, indicating that ATP may function via protein phosphorylation by protein kinase C.
Günther
T
T
Institute of Molecular Biology and Biochemistry, Free University of Berlin, Germany.
Vormann
J
J
D000255:Adenosine Triphosphate / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D017920:Antiporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D007099:Imipramine / Q000494:pharmacology; D066298:In Vitro Techniques; D008274:Magnesium / Q000097:blood*; D011802:Quinidine / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000097:blood*
D017920:Antiporters; C046250:sodium-magnesium antiporter; D000584:Amiloride; D000255:Adenosine Triphosphate; D012964:Sodium; D008274:Magnesium; D011802:Quinidine; D007099:Imipramine