Tissue-specific HSP70 response in animals undergoing heat stress.

Heatstroke is a multisystem disorder that can result in death. Activities that increase the rate of heat storage predispose an organism to thermal injury. Using a 72-kDa heat shock protein (HSP72) as a marker of thermal injury, we determined 1) which organs synthesize HSP in animals after hyperthermia and 2) whether a high heating rate (HHR) resulted in more HSP72 than a low heating rate (LHR). Rats were assigned to either control, HHR (0.166 degrees C/min), or LHR (0.045 degrees C/min) groups. Heat exposure ended when colonic temperature (Tc) reached 42 degrees C. Total time in the heat and thermal load (measured as the time an animal maintained a Tc > 40.4 degrees C) were significantly lower in HHR compared with LHR animals. Hyperthermia resulted in a tissue-specific increase in HSP72 in the liver, small intestine, and kidney, but not in the brain or quadriceps muscles. In addition, HHR animals showed significantly greater accumulation of HSP72 in the liver compared with animals in the LHR group. Thus HSP72 synthesis is tissue specific at high physiological temperatures and may identify a critical target tissue susceptible to early thermal damage.