In order to study the cytoprotective function of heat shock proteins (HSPs) in vivo, the effect of preinduction of HSPs by hyperthermia on acetic acid-induced colitis was investigated. Expression of 60-kDa, 72-kDa, and 90-kDa heat shock proteins (HSP60, HSP72, and HSP90, respectively) in rat colonic mucosa was investigated by Western blot analysis and immunohistochemical study before and after hyperthermia. Following pretreatment with or without hyperthermia, the rats received intrarectal infusion of various doses of acetic acid. The colonic mucosal damage was evaluated by macroscopic and microscopic assessments 24 hr after the intrarectal infusion of acetic acid. Expression of HSPs was significantly increased by hyperthermia in rat colonic mucosa. Immunohistochemical study also showed the increments of HSPs in the colonic mucosal cells after hyperthermia. Acetic acid-induced colitis was dramatically prevented by pretreatment with hyperthermia when HSP72 and HSP90 were preinduced. On the other hand, induction of HSP60 did not correlate with mucosal protection. Our findings suggest that HSP72 and HSP90 may have cytoprotective function against acetic acid-induced mucosal damage. These results may be important for understanding the mechanism of "adaptive cytoprotection" mediated by HSPs.