Thermotolerance and heat shock protein 72 (HSP 72) in primary cultured hepatocytes

To clarify the changes of stress fibers (SF), HSP 72 and cell viability (CV) by various grades of heat shock (HS) treatment in primary cultured hepatocytes, we applied immunofluorescence for actin filaments and HSP 72, and MTT assay and methylene blue assay to evaluate CV. HS at 43°C and 45°C induced the disappearance of SF before the loss of CV and this phenomenon was reversibly recovered, if the treatment was not lethal. Therefore, the change of SF was able to become a guideline of the reversible cell damage. Both MTT assay and methylene blue assay seemed to have good correlation but the MTT assay showed apparent differences in this study. The primary cultured hepatocytes treated at 43°C for 20min. became gradually thermotolerant and the maximum thermotolerance level was 8 to 12 hours following the conditioning treatment. Our results indicate that HSP 72 accumulated in the nucleoli plays important roles in the thermotolerance.