Objective   To investigate the effect of heat adaptation on cell cycles of human hepatoma cells.

  Methods   The 7721 cells were randomly divided into four groups, which were control group, heat adaptation group, heat exposure group, and heat adaptation+heat exposure group.The cell cycles were determined by flow cytometry.

  Results   The proportion of cells in G₀/G₁ phase in the group of heat acclimation+heat stress was significantl less than those of other groups(P < 0.05).The proportion of cells in G₂/M phase in the group of directly exposure to 43℃ was obviously less that that in the group of heat acclimation+heat stress(P < 0.05).The rate of cells in S phase in the group of heat acclimation+heat exposure was remarkably more than thos in the groups of the heat adatation only or control(P < 0.05).

  Conclusion   Heat adaptation could reduce the G₀/G₁ phase arrest, and improve the G₂/M phase arrest and S phase arrest.