THE RESPONSE OF CAMP AND DNA SYNTHESIS IN RAT OSTEOSARCOMA CELLS TO MECHANICALLY DEFORMED CULTURE DISHES

: The purpose of this research was to document the biochemical response of rat osteosarcoma cells (ROS 17/2.8) to mechanical stress in vitro. The influence of mechanical stress on ROS 17/2.8 cells was studied using a stress application device. Briefly, the device was fabricated by bonding an orthodontic expansion screw outside the bottom of a plastic culture dish with self-curing acrylic resin. Irreversible deformation of the culture dish was produced by activating an expansion screw. The resulting mechanical stress was transferred to the cells which attached to the culture dish. The response in terms of cyclic adenosine monophosphate (cAMP) of ROS 17/2.8 cells to mechanical stress was measured using a competitive protein-binding method. The effect of mechanical stress on cellular growth was assessed through the incorporation of 3H-thymidine after different periods of mechanical stress application. The results revealed that mechanical stress could increase the production of cAMP in ROS 17/2.8 cells at an early phase after stress stimulation. This change in the cAMP level was dependent on the duration of stress application, and the maximal response occurred when the mechanical stress was applied for one hour. Although the cellular incorporation of 3H-thymidine decreased 40-60% in ROS 17/2.8 cells subjected to mechanical stress for 1 hour, this reaction recovered from the inhibition effect to 80-85% of the baseline when the mechanical stress lasted for 24 hours. The observations in this study indicate that mechanical stress stimulates the production of cAMP and inhibits the 3H-thymidine incorporation of ROS 17/2.8 cells at an early phase of stress application.