Reversible regulation by magnesium of chick embryo fibroblast proliferation

Rubin, A. H.; Chu, Berbie M.

doi:10.1002/jcp.1040940103

Cited by 22 publications

(11 citation statements)

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“…Exposure of fibroblasts, endothelial, and epithelial cells to reduced [Mg 2þ ] e , inhibits cell proliferation whereas replacing Mg 2þ in the culture medium stimulates cell growth (Rubin and Berbie, 1978;Banai et al, 1990;Zhou and Kummerow, 1995). However, this postive correlation between Mg 2þ availability and degree of proliferation does not seem to be a homogeneous phenomenon.…”

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confidence: 96%

Modulation of vascular smooth muscle cell growth by magnesium—role of mitogen—activated protein kinases

Touyz

Yao

2003

Journal Cellular Physiology

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We tested the hypothesis that Mg(2+) influences growth of vascular smooth muscle cells (VSMCs) by modulating cell cycle activation through mitogen-activated protein (MAP) kinase-dependent pathways. Rat VSMCs were grown in culture medium containing normal Mg(2+) (1.02 mmol/L, control) and increasing concentrations of Mg(2+) (2-4 mmol/L) for 1-8 days. Effects of varying extracellular Mg(2+) concentration ([Mg(2+)](e)) on intracellular free Mg(2+) concentration ([Mg(2+)](i)) were assessed using mag-fura. Growth actions of Mg(2+) were evaluated by measuring cell cycle activation, DNA synthesis, and protein synthesis. Expression of cell cycle promoters, cyclin D1, cyclin E, Cdk2, and Cdk4 was assessed by immunoblotting. Phosphorylation of cell cycle inhibitors p21(cip1) and p27(kip1) and MAP kinases, ERK1/2, p38MAP kinase, and JNK was evaluated using phospho-specific antibodies. [Mg(2+)](i) increased in a dose-dependent manner in response to increasing [Mg(2+)](e). These effects were evident within 2 days and maximal responses were obtained after 6 days. High [Mg(2+)](e) induced cell cycle activation with a lower proportion of cells in G(1) phase (75 +/- 1.0%) and a higher fraction of cells in S phase (12 +/- 0.7%) versus control (G(1), 88.5 +/- 1.4%; S, 6.8 +/- 1.2%; P < 0.05). This was associated with increased protein content of cyclin D1 and Cdk4 and decreased activation of p21(cip1) and p27(kip1). In cells exposed to 2 mmol/L Mg(2+), DNA and protein synthesis was increased approximately threefold. Phosphorylation of MEK1/2 and ERK1/2 was enhanced two to threefold in cells grown in 2 mmol/L Mg(2+). These effects were rapid, occurring within 2 days. Phosphorylation of MEK3/6, p38 MAP kinase, and JNK was unaltered by increasing [Mg2](e). PD98059 (10(-5) mol/L), specific MEK1/2 inhibitor, but not SB202190 (10(-5) mol/L) (specific p38 MAP kinase inhibitor), attenuated Mg(2+)-induced growth actions. These data demonstrate the novel findings that cell cycle activation and growth regulation by Mg(2+) occurs via ERK1/2-dependent, p38 MAP kinase-independent pathways.

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confidence: 96%

Modulation of vascular smooth muscle cell growth by magnesium—role of mitogen—activated protein kinases

Touyz

Yao

2003

Journal Cellular Physiology

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“…The omission of either Ca2+ or Mg2+ from the medium of cultured cells inhibits metabolism and growth to varying degrees in different cell types (1)(2)(3)(4)(5)(6)(7). The effects of omitting one can be greatly intensified by reducing the concentration of the other (4,7,8), and it is not completely clear whether the two are interchangeable in some cellular function(s) or have separate roles.…”

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confidence: 99%

“…The effects of omitting one can be greatly intensified by reducing the concentration of the other (4,7,8), and it is not completely clear whether the two are interchangeable in some cellular function(s) or have separate roles. Our studies of the divalent cations have concentrated on their effects on the initiation of DNA synthesis, which is a delayed response of cells to external effectors and dependent on other cellular activities, including energy metabolism and the synthesis of RNA and protein (9).…”

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confidence: 99%

Separate roles for calcium and magnesium in their synergistic effect on uridine uptake by cultured cells: Significance for growth control

Bowen‐Pope¹,

Vidair²,

Sanui³

et al. 1979

Proc. Natl. Acad. Sci. U.S.A.

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The uptake of uridine by BALB/c3T3 cells is markedly inhibited by reducing the concentration of Mg2+ in medium containing only traces of Ca2+. When physiological [Ca2+J is present in the medium, omission of Mge+ has no effect on uridine uptake, and when Mg2+ is present, omission of Ca2+ has only a slight inhibitory effect. When both Ca2+ and Mg2+ are omitted, the concentration of Ca2+ in the cells is not reduced, but that of Mg2+ is reduced to about one-half in 3 hr. The concentration of K+ is also reduced, and that of Na+ is increased, suggesting increased membrane permeability to cations. 14; unpublished observation), a direct role for Mg2+ in regulating uridine uptake became highly plausible and a similar role for Ca2W unlikely. We decided to examine further the respective roles of the two ions in the regulation of uridine uptake because such a study promised to provide a clear-cut distinction between them. The basic strategy was to produce a powerful inhibition of uridine uptake by omitting both Ca2+ and Mg2+ from the medium and to observe the effect of restoring them singly or together. The effects of varying Na+ and K+ were also studied. The studies of uridine uptake were accompanied by measurements of the four major cations within the cells and of the cellular permeability to Lglucose. The results provide strong evidence for the direct role of Mg2+ in regulating uridine uptake and indicate the importance of Ca2+ in maintaining the permeability barrier of the cell. No evidence was found for a regulatory role of either Na+ or K+ in uridine uptake. MATERIALS AND METHODS Cell Culture and Labeling. BALB/c3T3 cells were maintained in modified Eagle's medium with 10% calf serum and labeled with [3H]thymidine as described (8). Except where noted, 60-mm polystyrene tissue culture dishes were used. After cultures had become confluent, they were switched to modified Eagle's medium with 1% serum overnight before use in experiments. In most experiments, cultures were labeled by addition of [3H]uridine (13.3 Ci/mmol, 1 Ci = 3.70 X 1010 Bq) for varying periods in the appropriate experimental medium and washed three times with ice-cold Tris-buffered saline. Acid-soluble material was extracted for 15 min with cold 5% trichloroacetic acid for scintillation counting. In the experiment of Fig. 1, however, cultures were washed five times by dipping in five successive beakers containing ice-cold 150 mM NaCl before extraction in trichloroacetic acid. The cultures were then dissolved in 0.1 M NaOH for subsequent measurement of protein content by the method of Lowry et al. (15) and, in the experiment of Fig. 6, of acid-insoluble radioactivity by scintillation counting.The uptake of L-glucose was measured in the various experimental media by addition of 5 ,uCi of L-[3H]glucose at tracer concentrations (10). After 20-40 min, the cultures were washed five times with Tris-buffered saline and material was extracted in cold 5% trichloroacetic acid for scintillation counting. Correction was made for extracellular label by sub...

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“…Additional support seemed to come from the finding that supranormal concentrations of Ca2+ stimulate the growth of quiescent 3T3 cells (12), but this has proven to be a nonspecific effect caused by insoluble complexes of Ca2+ and inorganic orthophosphate (Pi) (13,14). It has also been shown that Ca2+ deprivation in chick embryo cells causes a marked increase in the passive permeability of cells (15) and causes other changes that do not occur when cells are inhibited in a more physiological way by the withdrawal of serum or addition of cortisol (15,16 The procedures for measuring cation contents of cells by atomic absorption spectrophotometry were previously reported (20). Culture dishes (100 mm) were used in the cation determination experiments.…”

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Magnesium reverses inhibitory effects of calcium deprivation on coordinate response of 3T3 cells to serum

Rubin

Terasaki

Sanui

1978

Proc. Natl. Acad. Sci. U.S.A.

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When animal cells are stimulated to multiply by serum, hormones, or various other unrelated agents added to their culture medium, several early events occur, including acceleration in transport and phosphorylation of substrates (1, 2), energy metabolism (3), and synthesis of differentiated cell products (4, 5). After an extended lag period, the accelerated onset of DNA synthesis becomes manifest (6). This array of events has been designated the coordinate response to distinguish it from the "pleiotypic response," which explicitly excludes differentiated functions (7). We have shown that all the elements of the coordinate response can be inhibited in chick embryo cells in a reversible manner by lowering the [Mg2+] of the medium (8,9). From these results and several other considerations, we have proposed that variations in the availability of Mg2+ for transphosphorylation reactions within the cell mediate the coordinate response of cells to external effectors (8). Others have proposed that Ca2+ plays a central role in mediating the growth response of cells to external effectors (10). Support for a mediating role for Ca2+ is chiefly based on the observation that drastically lowering the [Ca2+] of the medium inhibits the onset of DNA synthesis and thereby limits the multiplication of cells (11). Additional support seemed to come from the finding that supranormal concentrations of Ca2+ stimulate the growth of quiescent 3T3 cells (12), but this has proven to be a nonspecific effect caused by insoluble complexes of Ca2+ and inorganic orthophosphate (Pi) (13,14). It has also been shown that Ca2+ deprivation in chick embryo cells causes a marked increase in the passive permeability of cells (15) The procedures for measuring cation contents of cells by atomic absorption spectrophotometry were previously reported (20). Culture dishes (100 mm) were used in the cation determination experiments. Briefly, the cultures were washed five times with 10 ml per wash of C02-free 0.25 M sucrose solution, 4379The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.

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Reversible regulation by magnesium of chick embryo fibroblast proliferation

Cited by 22 publications

References 28 publications

Modulation of vascular smooth muscle cell growth by magnesium—role of mitogen—activated protein kinases

Modulation of vascular smooth muscle cell growth by magnesium—role of mitogen—activated protein kinases

Separate roles for calcium and magnesium in their synergistic effect on uridine uptake by cultured cells: Significance for growth control

Magnesium reverses inhibitory effects of calcium deprivation on coordinate response of 3T3 cells to serum

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