The influence of local skin temperature on the sweat glands maximum ion reabsorption rate.

PURPOSE: Changes in mean skin temperature (Tsk) have been shown to modify the maximum rate of sweat ion reabsorption. This study aims to extend this knowledge by investigating if modifications could also be caused by local Tsk. METHODS: The influence of local Tsk on the sweat gland maximum ion reabsorption rates was investigated in ten healthy volunteers (three female and seven male; 20.8 ± 1.2 years, 60.4 ± 7.7 kg, 169.4 ± 10.4 cm) during passive heating (water-perfused suit and lower leg water immersion). In two separate trials, in a randomized order, one forearm was always manipulated to 33 °C (Neutral), whilst the other was manipulated to either 30 °C (Cool) or 36 °C (Warm) using water-perfused patches. Oesophageal temperature (Tes), forearm Tsk, sweat rate (SR), galvanic skin conductance (GSC) and salivary aldosterone concentrations were measured. The sweat gland maximum ion reabsorption rates were identified using the ∆SR threshold for an increasing ∆GSC. RESULTS: Thermal [Tes and body temperature (Tb)] and non-thermal responses (aldosterone) were similar across all conditions (p > 0.05). A temperature-dependent response for the sweat gland maximum ion reabsorption rates was evident between 30 °C (0.18 ± 0.10 mg/cm2/min) and 36 °C (0.28 ± 0.14 mg/cm2/min, d = 0.88, p < 0.05), but not for 33 °C (0.22 ± 0.12 mg/cm2/min), d = 0.44 and d = 0.36, p > 0.05. CONCLUSION: The data indicate that small variations in local Tsk may not affect the sweat gland maximum ion reabsorption rates but when the local Tsk increases by > 6 °C, ion reabsorption rates also increase.