An Na+-stimulated Mg2+-transport system in human red blood cells

A large Mg:* cell uptake against concentration gradients is stimulated in collagenase-disper~ed ra: myocytes by carbachol and in hepato~t~ by carbachol or vasoprcssin. The signalling pathway(s) responsible for this stimulation o1" Mg ~-+ uptake was inv.+stigated by using various activators or inhibitors of protein kinase C (PKC) and by correlatin/~ Mg :+ uptake with cell PKC activity and cAMP content. In both cell preparations, the dir~.,ct stimulation of PKC by diaeylglycerol analogs or phorbol esters reproduce the same pattern of MS -+" uptake as that induced by carbachol or vasopressin. These data indicate that the activation of PKC is responsible for a stimulation of Mg:" uptake by myocytes or hepatocytes, whereas increase in cAMP in these cells stimulates Mg a' release.

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“…In mammalian systems, plasma membrane Mg 2. transport appears to involve Na ÷ and/or other ion co-transport [14,15,36,37].…”

Section: Discussionmentioning

confidence: 99%

“…Evidence for a Na+-Mg 2. exchanger has been clearly documented in the literature [14,15], and a novel P-class ATPase inwardly transporting Mg 2. has recently been reported in bacteria [16,17].…”

Section: A Bbrevandtions: H Epes 4-(2-hydroxymethyl)l Piperazine Ethamentioning

confidence: 97%

Regulation of Mg²⁺ uptake in isolated rat myocytes and hepatocytes by protein kinase C

1992

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“…While Mg transport systems have only recently begun to be analyzed (see review by Flatman, 1991) it appears, at least in human red cells, that Mg is transported across the membrane by two different mechanisms. One mechanism is by an ATP-dependent Mgi/Nao exchanger and the other by passive diffusion (Feray and Garay, 1986;Ltidi and Schatzmann, 1987;Frenkel et al, 1989). The maximal rate for Mgi efflux (measured in the unsteady state) is ~ 0.2 mmol/liter cells per h, with the concentrations of Mg~ ~e and Nao giving half-maximal rates being ~ 1 and 8 raM, respectively (Ltidi and Schatzmann, 1987;Frenkel et al, 1989).…”

Section: Discussionmentioning

confidence: 99%

Internal magnesium, 2,3-diphosphoglycerate, and the regulation of the steady-state volume of human red blood cells by the Na/K/2Cl cotransport system.

Mairbäurl

Hoffman

1992

The Journal of General Physiology

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This study is concerned with the relationship between the Na/K/CI cotransport system and the steady-state volume (MCV) of red blood cells. Cotransport rate was determined in unfractionated and density-separated red cells of different MCV from different donors to see whether cotransport differences contribute to the difference in the distribution of MCVs. Cotransport, studied in cells at their original MCVs, was determined as the bumetanide (10 ~.M)-sensitive 2~Na efflux in the presence of ouabain (50 I~M) after adjusting cellular Na (Nai) and K~ to achieve near maximal transport rates. This condition was chosen to rule out MCV-related differences in Nai and Ki that might contribute to differences in the net chemical driving force for cotransport. We found that in both unfractionated and density-separated red cells the cotransport rate was inversely correlated with MCV. MCV was correlated directly with red cell 2,3-diphosphoglycerate (DPG), whereas total red cell Mg was only slightly elevated in cells with high MCV. Thus intraceUular free Mg (Mg~ e) is evidently lower in red cells with high 2,3-DPG (i.e., high MCV) and vice versa. Results from flux measurements at their original MCVs, after altering Mg[ r~ with the ionophore A23187, indicated a high Mgi sensitivity of cotransport: depletion of M~ r~ inhibited and an elevation of M~ tee increased the cotransport rate. The apparent K05 for Mg~ e" was ~ 0.4 mM. Maximizing Mig~ ~ at optimum Nai and I~ minimized the differences in cotransport rates among the different donors. It is concluded that the relative cotransport rate is regulated for cells in the steady state at their original cell volume, not by the number of copies of the cotransporter but by differences in Mig~ ~. The interindividual differences in Mg~ ~, determined primarily by differences in the 2,3-DPG content, are responsible for the differences in the relative cotransport activity that results in an inverse Address reprint requests to Dr.

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“…It has been reported that this procedure restores the cation impermeability of the red cell membrane and does not affect Mg 2+ efflux. 28 At the end of this period, erythrocytes were washed five times with cold KCI 150 mmol/L and resuspended in the same solution at a hematocrit of 20% to 25%. …”

Section: + Loading Proceduresmentioning

confidence: 99%

“…However, the demonstration of this point would require the difficult measurement of the effect of internal Mg 2+ on a * influx. 28 The ability of Mg 2+ to influence blood pressure may be related to the effect of Mg 2+ on the intracellular Na + and Ca 2+ metabolism. 39 Lower levels of intracellular Mg 2+ may exert an inhibitory effect on Na + and Ca 2+ pumps, enhance Ca 2+ release from sarcoplasmic reticulum, and contribute to the increased vascular tone.…”

Section: Clinical Aspectsmentioning

confidence: 99%

Increased activity of the Mg2+/Na+ exchanger in red blood cells from essential hypertensive patients.

et al. 1994

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An Na+-stimulated Mg2+-transport system in human red blood cells

Cited by 98 publications

References 15 publications

Regulation of Mg²⁺ uptake in isolated rat myocytes and hepatocytes by protein kinase C

Regulation of Mg²⁺ uptake in isolated rat myocytes and hepatocytes by protein kinase C

Internal magnesium, 2,3-diphosphoglycerate, and the regulation of the steady-state volume of human red blood cells by the Na/K/2Cl cotransport system.

Increased activity of the Mg2+/Na+ exchanger in red blood cells from essential hypertensive patients.

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An Na+-stimulated Mg2+-transport system in human red blood cells

Cited by 98 publications

References 15 publications

Regulation of Mg2+ uptake in isolated rat myocytes and hepatocytes by protein kinase C

Regulation of Mg2+ uptake in isolated rat myocytes and hepatocytes by protein kinase C

Internal magnesium, 2,3-diphosphoglycerate, and the regulation of the steady-state volume of human red blood cells by the Na/K/2Cl cotransport system.

Increased activity of the Mg2+/Na+ exchanger in red blood cells from essential hypertensive patients.

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Regulation of Mg²⁺ uptake in isolated rat myocytes and hepatocytes by protein kinase C

Regulation of Mg²⁺ uptake in isolated rat myocytes and hepatocytes by protein kinase C