title: Isothermic and fixed-intensity heat acclimation methods elicit equal increases in Hsp72 mRNA.
abstract: Thermotolerance, to which heat shock protein-72 (Hsp72) contributes, is an acquired state achieved following heat acclimation (HA), eliciting cellular adaption and protection against thermal stress. Optimal HA methods achieving the greatest heat shock response (HSR) are equivocal; therefore, investigation of methods provoking the greatest sustained HSR is required to optimize cellular adaptation. Twenty-four males performed short-term HA (STHA; five sessions) and long-term HA (LTHA; STHA plus further five sessions) utilizing fixed-intensity (FIXED; workload = 50% V ˙ O 2 p e a k ), continuous isothermic HA [ISOCONT ; target rectal temperature (Trec ) = 38.5 °C], or progressive isothermic HA (ISOPROG ; target Trec  = 38.5 °C for STHA then target Trec  = 39.0 °C for LTHA). Leukocyte Hsp72 mRNA was measured pre- and post day 1, day 5, and day 10 of HA via reverse transcription quantitative polymerase chain reaction to determine the HSR. Hsp72 mRNA increased (P < 0.05) pre- to post day 1, pre- to post day 5, and pre to post day 10 in FIXED, ISOCONT , and ISOPROG , but no differences were observed between methods (P > 0.05). The equal Hsp72 mRNA increases occurring from consistent, reduced, or increased endogenous strain following STHA and LTHA suggest that transcription occurs following attainment of sufficient endogenous criteria. These data give confidence that all reported HA methods increase Hsp72 mRNA and are capable of eliciting adaptations toward thermotolerance.
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Welkin Human Performance Laboratories, University of Brighton, Eastbourne, UK.
authors.forename: O R
authors.initials: OR
authors.lastname: Gibson
authors.forename: J A
authors.initials: JA
authors.lastname: Mee
authors.forename: L
authors.initials: L
authors.lastname: Taylor
authors.forename: J A
authors.initials: JA
authors.lastname: Tuttle
authors.forename: P W
authors.initials: PW
authors.lastname: Watt
authors.forename: N S
authors.initials: NS
authors.lastname: Maxwell
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D015415:Biomarkers / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D050884:HSP72 Heat-Shock Proteins / Q000097:blood / Q000235:genetics*; D006358:Hot Temperature; D006801:Humans; D007962:Leukocytes / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000097:blood*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D015415:Biomarkers; D050884:HSP72 Heat-Shock Proteins; D012333:RNA, Messenger
keywords: Thermoregulation; cellular stress response; heat illness; heat shock protein 72; heat stress; hyperthermia; thermotolerance