Fig. (4) ELF MF exposure increases alkaline phosphatase activity. SaOS-2 cells were exposed or not to ELF MF for 1 h and after 0, 4, and 24 h, ALP activity assays were carried out. Values are reported as 405 nm absorbance and are expressed as means of three independent experiments (each carried out with at least eight assay replicates) ± standard deviations.