The roles of K_(Ca), K_(ATP), and K_v channels in regulating cutaneous vasodilation and sweating during exercise in the heat

摘要

We recently showed the varying roles of Ca~(2+)-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: /) lactated Ringer solution (control); 2) 50 mM tetraethylammonium (nonspecific K_(ca) channel blocker); 5) 5 mM glybenclamide (selective Katp 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). Katp 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 Katp channels contribute to the regulation of cutaneous vasodilation during rest and/or exercise and recovery in the heat.