Effect of magnesium on secretion of platelet-derived growth factor by cultured human arterial smooth muscle cells.

Two conditioned media were prepared by culturing human umbilical artery smooth muscle cells (SMC) in 75 cm2 flasks with minimum essential medium (MEM) under magnesium (Mg) sufficient (900 microM) or deficient (100 microM) conditions for 72 h ([900]- and [100]-MEM), respectively. A third conditioned medium was obtained by adjusting the Mg concentration of half of the [100]-MEM to 900 microM ([100-900]-MEM). SMC in 12-well plates were incubated in one of the three conditioned media and the growth rates of SMC were determined by [3H]-thymidine incorporation and cell counting. The growth rate in [100-900]-MEM was significantly higher than in [900]- and [100]-MEM. When platelet derived growth factor (PDGF) was neutralized by the addition of a mixture of anti-PDGF-AA and -BB antibodies, [3H]-thymidine incorporation in [100-900]-MEM decreased by 23.3 per cent, but only by 7.0 per cent in [900]-MEM. The quantity of PDGF in the Mg-deficient media was greater than in the magnesium-sufficient media at all indicated times, as shown by radioimmunoassay for PDGF-BB or -AB. These results indicate that Mg deficiency increases the secretion of PDGF by SMC.