Characterization of magnesium efflux from Ehrlich ascites tumor cells.
Magnesium efflux from intact Ehrlich ascites tumor cells (EATC) has been characterized under 0-trans conditions. It is shown that a magnesium-extruding mechanism operates in these cells which brings about magnesium efflux up to 20% of the cell total content. EATC magnesium efflux is independent from extracellular Ca2+ and its apparent velocity is not affected by [Mg2+]o up to 160 microM. This extrusion, however, is strictly dependent on extracellular Na+ and it is inhibited by ouabain (1 mM), amiloride (1 mM), imipramine (0.5 mM) and quinidine (1 mM). It is not affected by HMA (5-N,N-hexamethylene) amiloride) (0.5 microM) and vanadate (0.1 mM). Bumetanide (0.5 mM) enhances magnesium extrusion in these cells. EATC magnesium extrusion can be significantly stimulated by db cAMP, forskolin, and IBX (3-isobutyl-1-methyl-xanthine). The intracellular magnesium distribution, studied also by means of the ionophore A23187, is regulated by energy metabolism and cell ATP content. Altogether our data demonstrate that EATC exhibit a magnesium extrusion sustained by Na+ gradient across the plasma membrane and carried out by a Na+/Mg2+ antiport. In these cells magnesium homoeostasis results, regulated efficiently by cell ATP and cAMP content.
Wolf
F I
FI
Institute of General Pathology, Catholic University, School of Medicine, Rome, Italy.
Di Francesco
A
A
Cittadini
A
A
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004734:Energy Metabolism; D005947:Glucose / Q000494:pharmacology; D006706:Homeostasis; D007099:Imipramine / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism*; D051379:Mice; D010042:Ouabain / Q000494:pharmacology; D011802:Quinidine / Q000494:pharmacology; D012402:Rotenone / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured
D012402:Rotenone; D002034:Bumetanide; C057360:5-(N,N-hexamethylene)amiloride; D005576:Colforsin; D000001:Calcimycin; D010042:Ouabain; D003994:Bucladesine; D000968:Antimycin A; D000584:Amiloride; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D008274:Magnesium; D011802:Quinidine; D005947:Glucose; D007099:Imipramine; D015056:1-Methyl-3-isobutylxanthine