COMBINED MAGNETIC-FIELDS INCREASE INSULIN-LIKE GROWTH FACTOR-II IN TE-85 HUMAN OSTEOSARCOMA BONE CELL-CULTURES

In vitro exposure to low-energy, combined magnetic fields (CMF) increa sed the release of insulin-like growth factor (IGF)-II from human TE-8 5 osteosarcoma cells. Short-term CMF exposure of only 10 min increased IGF-II levels in conditioned medium 1 h post CMF exposure. IGF-II lev els were measured with a radioreceptor assay using H-35 cells that con tain abundant IGF-II but not IGF-I receptors. This assay also uses a r ecently validated BioGel P-10 acid gel filtration method to remove IGF binding protein before quantitation of either IGF-I or IGF-II. In add ition to an increase in IGF-II levels, DNA synthesis, as an index of c ell proliferation, was increased during the 24-h period post CMF expos ure. A monoclonal antibody against IGF-II blocked the increase in cell proliferation following CMF exposure, whereas a control monoclonal an tibody against osteocalcin did not attenuate the mitogenic action of C MF exposure. The effect of CMF exposure to increase both cell prolifer ation and IGF-II was cell-density dependent with greater stimulation b y CMF observed at lower densities. Together, these data are consistent with the hypothesis that CMF exposure stimulates release/production o f IGF-II from bone cells and that increased IGF-II then promotes an in crease in cell proliferation.