Function of human eccrine sweat glands during dynamic exercise and passive heat stress.
ABSTRACT The purpose of this study was to identify the pattern of change in the density of activated sweat glands (ASG) and sweat output per gland (SGO) during dynamic constant-workload exercise and passive heat stress. Eight male subjects (22.8 +/- 0.9 yr) exercised at a constant workload (117.5 +/- 4.8 W) and were also passively heated by lower-leg immersion into hot water of 42 degrees C under an ambient temperature of 25 degrees C and relative humidity of 50%. Esophageal temperature, mean skin temperature, sweating rate (SR), and heart rate were measured continuously during both trials. The number of ASG was determined every 4 min after the onset of sweating, whereas SGO was calculated by dividing SR by ASG. During both exercise and passive heating, SR increased abruptly during the first 8 min after onset of sweating, followed by a slower increase. Similarly for both protocols, the number of ASG increased rapidly during the first 8 min after the onset of sweating and then ceased to increase further (P > 0.05). Conversely, SGO increased linearly throughout both perturbations. Our results suggest that changes in forearm sweating rate rely on both ASG and SGO during the initial period of exercise and passive heating, whereas further increases in SR are dependent on increases in SGO.
- SourceAvailable from: Miguel Araujo Carneiro-Júnior[Show abstract] [Hide abstract]
ABSTRACT: OBJECTIVE: To review possible peculiarities in biological mechanisms related to responses of thermoregulatory and specific sweat glands in exercise performed by children in hot environments. DATA SOURCES: Review of 47 articles published between 1960 and 2011 in the electronic databases MedLine and SciELO Brazil using the following key-words: 'children', 'heat', 'sweating', 'thermoregulation', 'sweat gland', and 'exercise', alone or in combination, in addition to a doctoral thesis about the subject. DATA SYNTHESIS: Pre-pubertal sweat rate during exercise is lower than among adults. Children have different thermoregulatory characteristics, with a small sweat output rate due to small sweat glands. High ratio between surface and body mass increases the absorption of heat during exercise under thermal stress in children, raising the risk of hyperthermia symptoms. However, great blood flow to skin contributes to the better control of thermal homeostasis in children. Small size of the gland, low cholinergic sensibility, low levels of circulating catecholamines during stress, and lack of androgenic hormone explain the occurrence of low elimination of sweat in exercises performed by children. CONCLUSIONS: Children present immature sweat glands. Thus, physical activity combined with high temperatures is not well-tolerated by children and youngsters, with great vulnerability to thermal injury. In the heat, strict control of fluid intake and attentive monitoring of weather conditions should have especial attention for the safe practice of exercises.Revista paulista de pediatria : orgao oficial da Sociedade de Pediatria de Sao Paulo. 03/2013; 31(1):104-110.
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ABSTRACT: Relatively few studies have investigated peripheral sweating mechanisms of long-distance runners. The aim of this study was to compare peripheral sweating mechanisms in male long-distance runners, and sedentary counterparts. Thirty six subjects, including 20 sedentary controls and 16 long-distance runners (with 7-12 years of athletic training, average 9.2±2.1 years) were observed. Quantitative sudomotor axon reflex testing (QSART) with iontophoresis (2 mA for 5 min) and 10% acetylcholine (ACh) were performed to determine axon reflex-mediated and directly activated (DIR, muscarinic receptor) sweating. Sweat onset time, sweat rate, number of activated sweat glands, sweat output per gland and skin temperature were measured at rest while maximum oxygen uptake (VO2max) were measured during maximal cycling. Sweat rate, activated sweat glands, sweat output per gland, skin temperature and VO2max were significantly higher in the trained runners than in the sedentary controls. Sweat onset time was significantly shorter for the runners. In the group of long-distance runners, significant correlations were found between VO2max and sweat onset time (r2 = 0.543, P<0.01, n = 16), DIR sweat rate (r2 = 0.584, P<0.001, n = 16), sweat output per gland (r2 = 0.539, P<0.01, n = 16). There was no correlation between VO2max and activated sweat glands. These findings suggest that habitual long-distance running results in upregulation of the peripheral sweating mechanisms in humans. Additional research is needed to determine the molecular mechanism underlying these changes. These findings complement the existing sweating data in long-distance runners.PLoS ONE 01/2014; 9(4):e93976. · 3.73 Impact Factor
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ABSTRACT: Bromodeoxyuridine (BrdU) has commonly been used for detecting of label-retaining cells (LRCs). To determine if there are LRCs and the distributions of LRCs in eccrine sweat glands, 20 newborn SD rats within 24 h after birth were injected intraperitoneally with 50 mg/kg/time BrdU four consecutive times at 2-h intervals, or twice daily at 2-h intervals for four consecutive days. Six weeks after the last BrdU injection, rats were sacrificed, and the hind footpads were harvested, fixed and embedded in paraffin. Five-micrometer thickness tissue sections were cut and the expression of BrdU was detected immunohistochemically. The results showed that BrdU(+) cells were scatteredly distributed in coiled secretory part and coiled duct, as well as the straight duct, but not the intraepidermal duct of eccrine sweat glands. In secretory part, besides secretory cells, myoepithelial cells showed label retaining. The percentage of BrdU(+) cells in eccrine sweat gland of rat footpads had no significant difference between the two injection methods of BrdU (50 mg/kg/time BrdU four consecutive times at 2-h intervals vs. 50 mg/kg/time BrdU twice daily at 2-h intervals for four consecutive days) (P > 0.05). The percentage of BrdU(+) cells in eccrine sweat glands (4.2 ± 1.3 %) was significantly higher than that in stratum basale of epidermis (0.5 ± 0.1 ‰) (P < 0.05). In conclusion, there were LRCs in eccrine sweat glands of rat footpads, and these LRCs might play important roles in the homeostasis of skin and its appendages.Archives for Dermatological Research 08/2013; · 2.71 Impact Factor