title: Heat acclimation attenuates physiological strain and the HSP72, but not HSP90α, mRNA response to acute normobaric hypoxia.
abstract: Heat acclimation (HA) attenuates physiological strain in hot conditions via phenotypic and cellular adaptation. The aim of this study was to determine whether HA reduced physiological strain, and heat shock protein (HSP) 72 and HSP90α mRNA responses in acute normobaric hypoxia. Sixteen male participants completed ten 90-min sessions of isothermic HA (40°C/40% relative humidity) or exercise training [control (CON); 20°C/40% relative humidity]. HA or CON were preceded (HYP1) and proceeded (HYP2) by a 30-min normobaric hypoxic exposure [inspired O2 fraction = 0.12; 10-min rest, 10-min cycling at 40% peak O2 uptake (V̇O2 peak), 10-min cycling at 65% V̇O2 peak]. HA induced greater rectal temperatures, sweat rate, and heart rates (HR) than CON during the training sessions. HA, but not CON, reduced resting rectal temperatures and resting HR and increased sweat rate and plasma volume. Hemoglobin mass did not change following HA nor CON. HSP72 and HSP90α mRNA increased in response to each HA session, but did not change with CON. HR during HYP2 was lower and O2 saturation higher at 65% V̇O2 peak following HA, but not CON. O2 uptake/HR was greater at rest and 65% V̇O2 peak in HYP2 following HA, but was unchanged after CON. At rest, the respiratory exchange ratio was reduced during HYP2 following HA, but not CON. The increase in HSP72 mRNA during HYP1 did not occur in HYP2 following HA. In CON, HSP72 mRNA expression was unchanged during HYP1 and HYP2. In HA and CON, increases in HSP90α mRNA during HYP1 were maintained in HYP2. HA reduces physiological strain, and the transcription of HSP72, but not HSP90α mRNA in acute normobaric hypoxia.
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Environmental Extremes Laboratory, University of Brighton, Welkin Human Performance Laboratories, Eastbourne, United Kingdom; o.r.gibson@brighton.ac.uk.
authors.forename: Oliver R
authors.initials: OR
authors.lastname: Gibson
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Environmental Extremes Laboratory, University of Brighton, Welkin Human Performance Laboratories, Eastbourne, United Kingdom; English Institute of Sport, EIS Performance Centre, Loughborough University, Loughborough, United Kingdom; and.
authors.forename: Gareth
authors.initials: G
authors.lastname: Turner
authors.affiliation: Muscle Cellular and Molecular Physiology (MCMP) and Applied Sport and Exercise Science (ASEP) Research Groups, Department of Sport Science and Physical Activity, Institute of Sport and Physical Activity Research (ISPAR), University of Bedfordshire, Bedfordshire, United Kingdom.
authors.forename: James A
authors.initials: JA
authors.lastname: Tuttle
authors.affiliation: Muscle Cellular and Molecular Physiology (MCMP) and Applied Sport and Exercise Science (ASEP) Research Groups, Department of Sport Science and Physical Activity, Institute of Sport and Physical Activity Research (ISPAR), University of Bedfordshire, Bedfordshire, United Kingdom.
authors.forename: Lee
authors.initials: L
authors.lastname: Taylor
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Environmental Extremes Laboratory, University of Brighton, Welkin Human Performance Laboratories, Eastbourne, United Kingdom;
authors.forename: Peter W
authors.initials: PW
authors.lastname: Watt
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Environmental Extremes Laboratory, University of Brighton, Welkin Human Performance Laboratories, Eastbourne, United Kingdom;
authors.forename: Neil S
authors.initials: NS
authors.lastname: Maxwell
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D001642:Bicycling / Q000502:physiology; D015444:Exercise / Q000502:physiology; D050884:HSP72 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D006801:Humans; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D012333:RNA, Messenger; D055815:Young Adult
chemical_list: D050884:HSP72 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D012333:RNA, Messenger
keywords: altitude; cardiovascular; cross-acclimation; cross-tolerance; heat stress; plasma volume