High temperature enhances cytotoxicity of mercury (HgCl2) on HeLa S3 cells.

The combined effect of mercury (HgCl2) and high temperature on the growth and synthesis of nucleic acid and protein, and on the cell cycle of HeLa S3 cells was investigated. The subsequent growth of the cells was dose-dependently inhibited by mercury at 37.2 degrees and 41.2 degrees C. The inhibitory effect of mercury on subsequent growth was enhanced at the higher temperature. IC50 values for DNA and RNA synthesis but not protein synthesis, at 41.2 degrees C, were significantly lower than those at 37.2 degrees C (P less than 0.05, P less than 0.01, respectively). Flow cytometric analysis using synchronous cells indicated the possibility of blocking of cell cycle progression in the early part of S phase by the combined treatment. These results suggest that the cytotoxicity of mercury to cell growth was enhanced at the higher temperature and that this enhancement is related to the increased inhibitory effect of mercury on DNA and RNA synthesis and on the cell cycle at high temperatures.