Purpose: The purpose of this study was to investigate the early effects of the cyclic uniaxial compressive stress on Stress70/GRP75 in the rat condylar chondrocyte.
Methods: The third-passage chondrocytes were harvested from the mandibular condyles of 2-day-old rats for this study, and a cellular compressive stress device (self-made four-point bending system, Patent No.01129166.4 & 01256849.x) was used to apply stress on cells at 4000 microstrain (0.5 Hz frequency) for 0, 15, 30, 60, 120, 240 minutes respectively. The early effects of the cyclic uniaxial compressive stress on Stress70/GRP75 in the rat mandibular condylar chondrocytes were examined by Western blot and image analysis. One-way ANOVA was used for statistical analysis.
Results: The results showed that the expression of Stress70/GRP75 changed significantly with 4000 microstrain compressive stress loading. The gray scale value of protein band at 0 minute was 114.2+/-5.08, significantly decreased to 86.1+/-5.09 (P<0.001) after 30 minutes, and then gradually increased to 104.0+/-4.41 (P<0.01) at 60 minutes. The expression of Stress70/GRP75 up-regulated to 134.5+/-3.74 (P<0.001) at 120 minutes, and continued to increase within 240 minutes.
Conclusion: There is time-dependent response between the 4000 microstrain compressive stress stimulate and Stress70/GRP75. The expression of Stress70/GRP75 inhibited initially under the compressive stress, and then increased by feedback with the increased loading time.