The Roles of the Na+/K+-ATPase, NKCC, and K+ Channels in the Regulation Local Sweating and Cutaneous Blood Flow During Exercise in Humans in vivo

Abstract

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 cotransporter (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 semi-recumbent cycling bouts at low (30% VO2peak), moderate (50% VO2peak), and high (70% VO2peak) intensity exercise, 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 mᴍ ouabain (Na+/K+-ATPase inhibitor), 3) 10 mᴍ bumetanide (NKCC inhibitor), or 4) 50 mᴍ BaCl2 (non-specific 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 exercise.