Leukocyte Hsp72 mRNA Transcription Does Not Differ Between Males and Females During Heat Acclimation

Purpose: Thermotolerance is an acquired state of increased cytoprotection achieved following single
or repeated exposures to heat stress, in part characterised by changes in the intracellular 72kda heat
shock protein (HSP72; HSPA1A). Females have demonstrated reduced exercise induced HSP72 in
comparison to males. This study examined sex differences in heat shock protein 72 messenger
ribonucleic acid (Hsp72 mRNA) transcription during heat acclimation (HA) to identify whether sex
differences were a result of differential gene transcription.
Methods: Ten participants (5M, 5F) performed ten, 90 min controlled hyperthermia [rectal
temperature (Tre) ≥ 38.5°C] HA sessions over 12 d. Leukocyte Hsp72 mRNA was measured pre and
post D1, D5, and D10, via Reverse transcription polymerase chain reaction (RT-QPCR).
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Results: HA was evidenced by a reduction in resting Tre (-0.4 ± 0.5°C) and resting heart rate [(HR); -13
± 7 beats.min-1] following HA (p ≤ 0.05). During HA no difference (p > 0.05) was observed in ΔTre
between males (D1 = 1.5 ± 0.2°C; D5 = 1.6 ± 0.4°C; D10 = 1.8 ± 0.3°C) and females (D1 = 1.5 ± 0.5°C;
D5 = 1.4 ± 0.2°C; D10 = 1.8 ± 0.3°C). This was also true of mean Tre demonstrating equality of thermal
stimuli for mRNA transcription and HA. There were no differences (p > 0.05) in Hsp72 mRNA
expression between HA sessions or between males (D1 = +1.8 ± 1.5 fold; D5 = +2.0 ± 1.0 fold; D10 =
+1.1 ± 0.4 fold) and females (D1 = +2.6 ± 1.8 fold; D5 = +1.8 ± 1.4 fold; D10 = +0.9 ± 1.9 fold).
Conclusions: This experiment demonstrates that there is no difference in Hsp72 mRNA increases
during HA between sexes when controlled hyperthermia HA is utilised. Gender specific differences in
exercise-induced HSP72 reported elsewhere likely result from post-transcriptional events.