Effects of infrasound on biological characteristics of osteoblast-like cells

Aim: To observe the effects of infrasound of different frequencies under 100 dB on biological characteristics such as proliferation and secretaries function etc. of osteoblast-like cells in mice. Methods: The experiment was conducted in the Department of Radiobiology of Fourth Military Medical University of PLA from March to June 2005. After primary culture, cells were randomly divided into blank control group, 4 Hz 100 dB group, 12 Hz 100 dB group and 20 Hz 100 dB group. Frozed cell stains reanimated and cells in logarithmic growth phase were selected and inoculated into 48-pore cultivating board at the concentration of 1×107 L-1. A total of 4 boards were inoculated into and cells were adhere to the walls. From 8 PM of the next day, cells of each group were exposed to infrasound. Cells in the 4 Hz 100 dB group, 12 Hz 100 dB group and 20 Hz 100 dB group were exposed to infrasound at corresponding frequencies and that of sound pressure level (SPL) parameter; Cells in the blank control group were exposed to infrasound without output for 5 days and 30 minutes each day. Cellular proliferation was calculated, and alkaline phosphatease activities (APA) and changes of expression of osteocalcin (OC) in osteoblast-like cells of mice exposed to infrasound were observed after 5 days. Results: 1 Effects of infrasound of different parameters on osteoblast-like cells of mice: Osteoblast-like cells were in irregular polygons, which did not changed obviously after being exposed to infrasound. 5 days after exposure, densities of osteoblast-like cells in mice of 4 Hz 100 dB group, 12 Hz 100 dB group and 20 Hz 100 dB group were remarkably higher than those in the blank control group [(52.25±8.52), (50.33±7.99), (49.82±7.05), (39.92±7.38)107 L-1,P < 0.05]. 2 Expressions of OC in osteoblast-like cells of mice after being exposed to infrasound: At 5 days after exposure, concentrations of OC of osteoblast-like cells in mice of 4 Hz 100 dB group, 12 Hz 100 dB group and 20 Hz 100 dB group were markedly higher than those in the blank control group [(1.401 2±0.531 9), (0.877 5 ±0.258 9), (2.257 5±0.830 7), (0.592 5±0.172 5) μg/L;P=0.001, 0.023, 0.000 5]. 3 Changes of APA in osteoblast-like cells of mice after being exposed to infrasound: 5 days after exposure, expressions of APA in osteoblast-like cells of each group were lower, and absorption value in 4 Hz 100 dB group, 12 Hz 100 dB group, 20 Hz 100 dB group and blank control group were essentially similar (0.016±0.008,0.013±0.005,0.014±0.005, 0.013±0.005, P=0.92,1.0,0.95). Conclusion: Infrasound of 4,12 Hz 100 dB can significantly promote cell proliferation, and that of growth and 20 Hz 100 dB has an marked effect on secretion of OC, which suggests that in different frequency, proliferation in vitro and secretion function of osterblast-like cells can be promoted by being exposed to infrasound of 100 dB.