The roles of the Na(+)/K(+)‐ATPase, NKCC, and K(+) channels in regulating local sweating and cutaneous blood flow during exercise in humans in vivo

Na(+)/K(+)‐ATPase has been shown to regulate the sweating and cutaneous vascular responses during exercise; however, similar studies have not been conducted to assess the roles of the Na‐K‐2Cl co‐transporter (NKCC) and K(+) channels. Additionally, it remains to be determined if these mechanisms underpinning the heat loss responses differ with exercise intensity. Eleven young (24 ± 4 years) males performed three 30‐min semirecumbent cycling bouts at low (30% VO (2peak)), moderate (50% VO (2peak)), and high (70% VO (2peak)) intensity, respectively, each separated by 20‐min recovery periods. Using intradermal microdialysis, four forearm skin sites were continuously perfused with either: (1) lactated Ringer solution (Control); (2) 6 mmol·L(−1) ouabain (Na(+)/K(+)‐ATPase inhibitor); (3) 10 mmol·L(−1) bumetanide (NKCC inhibitor); or (4) 50 mmol·L(−1) BaCl(2) (nonspecific K(+) channel inhibitor); sites at which we assessed local sweat rate (LSR) and cutaneous vascular conductance (CVC). Inhibition of Na(+)/K(+)‐ATPase attenuated LSR compared to Control during the moderate and high‐intensity exercise bouts (both P ˂ 0.01), whereas attenuations with NKCC and K(+) channel inhibition were only apparent during the high‐intensity exercise bout (both P ≤ 0.05). Na(+)/K(+)‐ATPase inhibition augmented CVC during all exercise intensities (all P ˂ 0.01), whereas CVC was greater with NKCC inhibition during the low‐intensity exercise only (P ˂ 0.01) and attenuated with K(+) channel inhibition during the moderate and high‐intensity exercise conditions (both P ˂ 0.01). We show that Na(+)/K(+)‐ATPase, NKCC and K(+) channels all contribute to the regulation of sweating and cutaneous blood flow but their influence is dependent on the intensity of dynamic exercise.