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

Changes in mean skin temperature (T_sk) 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 T_sk.

The influence of local T_sk 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 (T_es), forearm T_sk, 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.

Thermal [T_es and body temperature (T_b)] 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.

The data indicate that small variations in local T_sk may not affect the sweat gland maximum ion reabsorption rates but when the local T_sk increases by > 6 °C, ion reabsorption rates also increase.