Regulation of Na+/Mg2+ antiport in rat erythrocytes.
In rat erythrocytes, the regulation of Na+/Mg2+ antiport by protein kinases (PKs), protein phosphatases (PPs), intracellular Mg2+, ATP and Cl- was investigated. In untreated erythrocytes, Na+/Mg2+ antiport was slightly inhibited by the PK inhibitor staurosporine, slightly stimulated by the PP inhibitor calyculin A and strongly stimulated by vanadate. PMA stimulated Na+/Mg2+ antiport. This effect was completely inhibited by staurosporine and partially inhibited by the PKC inhibitors Ro-31-8425 and BIM I. Participation of other PKs such as PKA, the MAPK cascade, PTK, CK I, CK II, CAM II-K, PI 3-K, and MLCK was excluded by use of inhibitors. Na+/Mg2+ antiport in rat erythrocytes can thus be stimulated by PKCalpha. In non-Mg2+ -loaded erythrocytes, ATP depletion reduced Mg2+ efflux and PMA stimulation in NaCl medium. A drastic activation of Na+/Mg2+ antiport was induced by Mg2+ loading which was not further stimulated by PMA. Staurosporine, Ro-31-8425, BIM I and calyculin A did not inhibit Na+/Mg2+ antiport of Mg2+ -loaded cells. Obviously, at high [Mg2+]i Na+/Mg2+ antiport is maximally stimulated. PKCalpha or PPs are not involved in stimulation by intracellular Mg2+. ATP depletion of Mg2+ -loaded erythrocytes reduced Mg2+ efflux and the affinity of Mg2+ binding sites of the Na+/Mg2+ antiporter to Mg2+. In non-Mg2+ -loaded erythrocytes Na+/Mg2+ antiport essentially depends on Cl-. Mg2+ -loaded erythrocytes were less sensitive to the activation of Na+/Mg2+ antiport by [Cl-]i.
Ebel
H
H
Campus Benjamin Franklin, Institut für Klinische Physiologie, Charité-Universitätsmedizin Berlin, Hindenburgdamm 30, D-12200, Germany. hans.ebel@charite.de
Kreis
R
R
Günther
T
T
D000818:Animals; D017920:Antiporters / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004912:Erythrocytes / Q000378:metabolism*; D007473:Ion Channels / Q000502:physiology; D020935:MAP Kinase Signaling System; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000502:physiology; D011494:Protein Kinases / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D050053:TRPM Cation Channels; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D017920:Antiporters; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D050053:TRPM Cation Channels; C046250:sodium-magnesium antiporter; D011494:Protein Kinases; C486584:Trpm7 protein, rat; D017868:Cyclic AMP-Dependent Protein Kinases; D008274:Magnesium; D013755:Tetradecanoylphorbol Acetate