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

Abstract Na + /K + ‐ ATP ase 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 + ‐ ATP ase 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 + ‐ ATP ase 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 + ‐ ATP ase 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 + ‐ ATP ase, 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.