The roles of KCa, KATP, and KV channels in regulating cutaneous vasodilation and sweating during exercise in the heat

We recently showed the varying roles of Ca²⁺-activated (K_Ca), ATP-sensitive (K_ATP), and voltage-gated (K_V) K⁺ channels in regulating cholinergic cutaneous vasodilation and sweating in normothermic conditions. However, it is unclear whether the respective contributions of these K⁺ channels remain intact during dynamic exercise in the heat. Eleven young (23 ± 4 yr) men completed a 30-min exercise bout at a fixed rate of metabolic heat production (400 W) followed by a 40-min recovery period in the heat (35°C, 20% relative humidity). Cutaneous vascular conductance (CVC) and local sweat rate were assessed at four forearm skin sites perfused via intradermal microdialysis with: 1) lactated Ringer solution (control); 2) 50 mM tetraethylammonium (nonspecific K_Ca channel blocker); 3) 5 mM glybenclamide (selective K_ATP channel blocker); or 4) 10 mM 4-aminopyridine (nonspecific K_V channel blocker). Responses were compared at baseline and at 10-min intervals during and following exercise. K_Ca channel inhibition resulted in greater CVC versus control at end exercise (P = 0.04) and 10 and 20 min into recovery (both P < 0.01). K_ATP channel blockade attenuated CVC compared with control during baseline (P = 0.04), exercise (all P ≤ 0.04), and 10 min into recovery (P = 0.02). No differences in CVC were observed with K_V channel inhibition during baseline (P = 0.15), exercise (all P ≥ 0.06), or recovery (all P ≥ 0.14). With the exception of K_V channel inhibition augmenting sweating during baseline (P = 0.04), responses were similar to control with all K⁺ channel blockers during each time period (all P ≥ 0.07). We demonstrated that K_Ca and K_ATP channels contribute to the regulation of cutaneous vasodilation during rest and/or exercise and recovery in the heat.

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