earticle

영어

For tropical inhabitants, it was shown that heat tolerance was characterized by suppressed sweating, which is completely distinguishable from adaptation to temporary exposure to heat. Therefore, we examined body temperature, sudomotor activity and serum levels of thermoregulation-related molecules including PGE2, COX-2, and orexin before and after heat acclimation (HA). Nine healthy male college students were enrolled in the study. The subjects were exposed to half-body immersion in hot water at the same time of day (2-5 pm) for 3 weeks. The HA protocol included 10 bouts of 30 min immersion. Water temperature was maintained at 42 ± 0.5°C, and trials were conducted on alternate days. During these procedures, the climatic chamber was maintained at 26.0 ± 0.5°C, with a relative humidity of 60 ± 3.0%, and air velocity < 1 m/sec. Tympanic and mean body temperature decreased by 0.15℃ (p<0.05) and 0.16℃ (p<0.05), respectively, after HA. Local sudomotor activities consist of sweat onset time, local sweating rates (SR), sweat volume (SV), activated sweat glands density (ASGD), and sweat output per single gland (SOPS) in four body parts (chest, abdomen, upperback, thigh). There was an increase in local sweat onset time, but there was a decrease in local SR, SV, and SOPS after HA. And PGE2, COX-2 level significantly decreased respectively (p<0.001), (p<0.01). Orexin level significantly decreased (p<0.01). Changes in body temperature were significantly correlated with changes in serum PGE2 (r2=0.495, p<0.001), COX-2 (r2=0.369, p<0.001), orexin (r2=0.382, p<0.001). In conclusion, decreased basal body temperature and serum levels of PGE2, COX-2, orexin, and the local sweat responses after HA. Our data suggest that decreased body temperature after HA was associated with decreases in thermoregulation molecules, which appears contribute to reduction of sudomotor activity under the heat load.