A comparison of thermal responses of human and rodent cells.

A comparison of heat responses of cells from human and rodent tumors indicates the following: (1) human cells appear to be appreciably more heat-resistant than are rodent cells in the range 41-45 degrees C; (2) while rodent cells show a marked increase in sensitivity as the temperature is increased from 42 and 43 degrees C, this change occurs at approximately 44 degrees C or higher for the human lines examined; (3) rodent cells are unable to acquire thermotolerance during exposure to 43 degrees C; the human cells do so readily; (4) decay of tolerance tends to be complete in 72 h in rodent cells; in human cells it may take twice that time. These results may have important implications for the clinical use of hyperthermia.