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

Abstract

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.

Magnesium and phosphate enrichment of culture medium stimulates the proliferation of epidermal cells from newborn and adult mice

“…A similar conclusion has been reached by Rubin et al (1978) in cultures of mouse fibroblasts exposed to high magnesium concentrations in a calcium-deprived medium. Magnesium may also exert its stimulatory effects on keratinocyte proliferation by affecting the organization of the cytoskeleton (Howard and Timasheff, 1988) or by improving cell-matrix interactions (Attramadal, 1969;Ruoslahti and Pierschbacher, 1987;Yasuda, 1974).…”

“…As opposed to its effect on mouse epidermal cell cultures, reduction of extracellular calcium (<0.02 mM) markedly inhibited the initiation of DNA synthesis in the fibroblast cell cultures. This inhibition was abolished by increasing the magnesium content of the medium (Rubin et al, 1978). The present results suggest that magnesium, added to a low calcium-containing medium, can complement the reduced calcium in enhancing the proliferation of mouse keratinocytes.…”

Magnesium in Man: Implications for Health and Disease

“…Over the last 40 years, the role of Mg 2ϩ in cell cycle control, protein synthesis, and growth factor response has been extensively studied, pioneered by several groundbreaking studies from the group of Harry Rubin (428,430). Cell proliferation is largely dependent on protein synthesis, more than DNA or RNA synthesis.…”

Cell cycle-dependent regulation of store-operated ICRAC and Mg2+-nucleotide-regulated MagNuM (TRPM7) currents

“…Early work by Rubin suggested that Ca 2+ and Mg 2+ synergize in cell growth and proliferation [40]. Another group proposed that extracellular Mg 2+ is essential for progression of WI-38 fibroblast from G1 into S phase [41].…”