IGF-II RECEPTOR NUMBER IS INCREASED IN TE-85 OSTEOSARCOMA CELLS BY COMBINED MAGNETIC-FIELDS

Human osteosarcoma-derived osteoblast-like cells, TE-85, were used to assess the effect of a lo rv frequency alternating magnetic field in c ombination with a controlled static magnetic field (combined magnetic fields, CMF) on insulin-like growth factor receptor regulation. In our culture system, application of a 15.3 Hz CMF induces a calculated max imum electrical potential in the culture media of 10(-5) V/m. Initial characterization of TE-85 cells demonstrated that (a) TE-85 cells cont ain both type I insulin-like growth factor (IGF-I) and IGF-II receptor s and (b) dose dependence for IGF-stimulated cell proliferation,vere c omparable to the affinities of the IGFs binding to membrane binding si tes (i.e., receptors had dissociation constants in the low nanomolar c oncentration range). The studies with CMF exposure revealed that CMF t reatment for 30 minutes increased the number of IGF-II receptors in a frequency-dependent manner without affecting the number of IGF-I recep tors. The CMF-dependent increase in IGF-II receptor number was associa ted with a significant increase in the IGF-II dissociation constant. T hese results indicate that membrane receptor levels can be altered by short-term exposure to low-energy, low-frequency electromagnetic field s and suggest a potential biochemical mechanism for electromagnetic ef fects on bone formation and remodeling.