IGF-II receptor number is increased in TE-85 osteosarcoma cells by combined magnetic fields

Abstract

Human osteosarcoma–derived osteoblast-like cells, TE-85, were used to assess the effect of a low frequency alternating magnetic field in combination 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 maximum electrical potential in the culture media of 10⁻⁵ V/m. Initial characterization of TE-85 cells demonstrated that (a) TE-85 cells contain both type I insulin-like growth factor (IGF-I) and IGF-II receptors and (b) dose dependence for IGF-stimulated cell proliferation were comparable to the affinities of the IGFs binding to membrane binding sites (i.e., receptors had dissociation constants in the low nanomolar concentration range). The studies with CMF exposure revealed that CMF treatment for 30 minutes increased the number of IGF-II receptors in a frequency-dependent manner without affecting the number of IGF-I receptors. The CMF-dependent increase in IGF-II receptor number was associated with a significant increase in the IGF-II dissociation constant. These results indicate that membrane receptor levels can be altered by short-term exposure to low-energy, low-frequency electromagnetic fields and suggest a potential biochemical mechanism for electromagnetic effects on bone formation and remodeling.